Help: Fuel pressure problems? - 1997 S351

Kenny · #1 09-13-2010

1997 S351 Vortec supercharged, 8psi.....Changed fuel filter a couple days ago. Fired it up, seemed to prime OK but my fuel pressure drops from 40psi at idle to 20 psi when I press the throttle under load. I replaced the pump in the tank with a Walbro 255 lph unit but still have the same problem. I also have a Vortech T rex external pump which was installed 10 years ago. It comes on for 2-3 seconds when the key is turned on so it is not dead. Is there a priming procedure I still need to do? I had NO problems until I replaced the filter.

S351r · #2 09-14-2010

You will most likely have to flush your fuel lines and fuel tank. While you have the tank out make sure nothing is wrong with the 255. Also, just because the T-rex comes on doesn't mean it is working correctly.

ctann · #3 09-14-2010

Quote:

Originally Posted by Kenny

1997 S351 Vortec supercharged, 8psi.....Changed fuel filter a couple days ago. Fired it up, seemed to prime OK but my fuel pressure drops from 40psi at idle to 20 psi when I press the throttle under load. I replaced the pump in the tank with a Walbro 255 lph unit but still have the same problem. I also have a Vortech T rex external pump which was installed 10 years ago. It comes on for 2-3 seconds when the key is turned on so it is not dead. Is there a priming procedure I still need to do? I had NO problems until I replaced the filter.

I had similar symptoms with my '98 S281 with a similar setup to yours, replacing the T-Rex fixed the issue. Mine had (AFAIK) the stock Ford pump in the tank. I'm not sure why they built the systems with the 2 pumps in line - perhaps they just leave the Ford pump to prime the T-Rex? It seems to me that putting two pumps in series just doubles your chances for problems (and makes it more difficult to diagnose when problems occur).

Chris.

Kenny · #4 09-14-2010

Well, the trex pump was the problem. For some reason, it was fine before the filter change and failed after the filter swap. It was blocking the new 255lph I installed in the tank. I guess the trex should have been primed seperately. I will run just the 255 for now. I think it is good to 500 rwp.

G8rDuc · #5 10-14-2010

Don't trust a 255 to support 500rwhp. You need to add a helper, get a boost-a-pump or something else in there.

S351r · #6 10-14-2010

The 255 won't handle 500 rwhp in blown applictaions. You need the T-rex.

uneedav8 · #7 11-14-2010

I would keep the inline also....

psi365 · #8 08-07-2012

I know I'm bring back a dead thread, but my 94 seems to be doing the same thing as the op's car was. Under heavy throttle I get 4psi of boost and I can watch my fuel pressure guage go to around 20psi. Just like the op I just replaced my fuel pump with a 255lph (it already had one actually) and the fuel filter. I can't say how well the car ran before cause it had sat for a long period of time before I bought it so I drained the old gas out and cleaned the fuel lines.

So do I need to replace the T Rex or is there some sort of priming procedure? If there is a priming procedure what is it?

G8rDuc · #9 08-07-2012

There's no priming procedure. You key on, you hear the pump prime (probably will need to key on several times since the fuel system needs to be filled and pressurized). If you still get low FP under boost, then you need to replace the t-rex or add a Boost-a-pump.

psi365 · #10 08-07-2012

I replaced the in tank pump and cycled the key until I saw fuel pressure on the fuel pressure guage. Sounds like I need a new T Rex then.

When does the T Rex come on? Is it always on or does it cycle on as needed?

G8rDuc · #11 08-07-2012

T-Rex is always on. You should hear it humming if you start the car.

psi365 · #12 08-07-2012

Great thanks for the information!! I just hope this is the reason why my car isn't making power. If it isn't I'm running out of ideas.

G8rDuc · #13 08-07-2012

If it's on a dyno with a wideband, you can tell if it's a fuel related issue. Could be any number of things, from the regulator to the pump to the injectors. The 94-96 cars also ran VERY lean (dangerously), so that has to be taken into consideration.

psi365 · #14 08-07-2012

Quote:

Originally Posted by G8rDuc

If it's on a dyno with a wideband, you can tell if it's a fuel related issue. Could be any number of things, from the regulator to the pump to the injectors. The 94-96 cars also ran VERY lean (dangerously), so that has to be taken into consideration.

The previous owner had it tuned. I just installed an Aeromotive adjustable fuel pressure regulator and a new Walbro 255lph in tank pump.

G8rDuc · #15 08-07-2012

I would return the FPR, those Aeromotive units are junk. There's not too much you really want to adjust with the FPR anyways. Put the stock unit back in and get it tuned with a programmer or a chip burned. Unless that car was modified, the stock program should be fine that it came with.

S351r · #16 08-10-2012

Just a fyi, the 94-96 stock programs are junk from Saleen.

psi365 · #17 08-10-2012

I know Scott. I sent you a picture of the retune dyno results and you told me the new tune is good to go. I'm slowly chipping away at the problems with this car. I hope my new T Rex came in today and I'll put it on tomorrow and see what happens.

Saleen_S351 · #18 08-13-2012

I am not familiar with the fuel system setup on the Saleens. Did they all come with a T-Rex? I am about to change my fuel filter but shying away with doing so based on what i'm reading here. If I change it at least i'll know where to start. I'll ask more where this T-Rex is located if I run into the same trouble. Thanks everyone :-)

psi365 · #19 08-14-2012

Quote:

Originally Posted by Saleen_S351

I am not familiar with the fuel system setup on the Saleens. Did they all come with a T-Rex? I am about to change my fuel filter but shying away with doing so based on what i'm reading here. If I change it at least i'll know where to start. I'll ask more where this T-Rex is located if I run into the same trouble. Thanks everyone :-)

To my knowledge (and I'm still new to Saleen's also) all R codes came with a T Rex from Saleen. It is an inline fuel pump which is located under the to the front of the spare tire well. The fuel filter is to the passenger side of the T Rex. Mine not working had nothing to do with changing the fuel filter. When I installed the new T Rex it also didn't work. I found that I had 0 volts at the Rex. I then went to the relay and found I had 0 volts there. I actually found that the previous owner for unknown reasons had unplugged the power wire to the relay. That was a nice $250 mistake.

99S351 · #20 08-14-2012

I think they did away with the T Rex booster pump in the later year cars. The stock intank pumps were upgraded to 255lph pumps and the cars got 36# injectors. This was enough to supply fuel for the stock HP level. The earlier cars still had a FMU and a booster pump to supplement the stock 190lph pumps. Later on, the cars ECM was tuned to control the fuel needs better than a FMU could and bigger injectors and pumps helped even more.

psi365 · #21 08-14-2012

According to 87vert all R codes had T Rex's from 94-96. After that is exactly as 99S351 described. So that means your 98 has zero chance for ruining it.

S351r · #22 08-14-2012

The later cars had t-rex's also. Both my 99's do. One has 3800 miles on it. The 255work by itself if borderline for a healthy 99. So are the 42's. You can push the injectors a little further but, they are operating at over 100%.

99S351 · #23 08-14-2012

I havent seen a T Rex on mine nor have I heard it. Not saying its not there, just havent seen it and Ive been under the car when its on a lift. Is it boost activated through a pressure switch? Come to think of it, the reason I may not have seen it is because of the cover thats over the fuel tank on the 99s. I think I'll pull my spare tire out and see if I see the mounting screws and can find the relay. Ive heard these pumps on a couple of my friends 94-95 Vortech cars but I havent heard that sound on mine. Wonder if its working. Seems to drive fine but I drive it fairly easy. Now Im curious lol. Im going to do some research now.

99S351 · #24 08-14-2012

Ok a little bit ago, I opened my trunk, took the spare tire out and inspected the wheel well where most T Rex pumps were mounted. There is no sign of mounting hardware or a relay wiring in my spare tire well. Either Saleen mounted it somewhere else or I dont have one. When I start the car, all I hear is the in tank pump too. From what I remember, T Rex's are a little loud lol

S351r · #25 08-15-2012

The t-rex is usually in front of the fuel tank. I'll verify that both my 99's have them when i get a chance.

99S351 · #26 08-15-2012

I talked to Mark L today at Performance Autosport and asked him about this pump. He wasnt sure if they had one or not and said all these cars are different. We talked about it being hidden by the tank shield so it could be hard to see but he didnt remember hearing one running when you turned the key on either and he's owned a few of these. Scott, he told me to tell you hello. So now this quest is a little more interesting now lol. Im gonna have to get mine on a lift and check it out a little closer or if you get a chance Scott, let us know where this pump is mounted. Thanks!

Saleen_S351 · #27 08-16-2012

Quote:

Originally Posted by 99S351

I talked to Mark L today at Performance Autosport and asked him about this pump. He wasnt sure if they had one or not and said all these cars are different. We talked about it being hidden by the tank shield so it could be hard to see but he didnt remember hearing one running when you turned the key on either and he's owned a few of these. Scott, he told me to tell you hello. So now this quest is a little more interesting now lol. Im gonna have to get mine on a lift and check it out a little closer or if you get a chance Scott, let us know where this pump is mounted. Thanks!

Awesome, more good info.

Saleen_S351 · #28 08-16-2012

Quote:

Originally Posted by psi365

According to 87vert all R codes had T Rex's from 94-96. After that is exactly as 99S351 described. So that means your 98 has zero chance for ruining it.

Awesome! This is all great to know. Thank you!

ricksaleen · #29 08-20-2012

All 94-99 S351Rs came with the base Vortech 351 Supercharger kit pieces which included the T-Rex Boost-A-Pump (External) located in front of the fuel tank (between tank and axle) and an inline 255 in the tank (Internal) hence the Dual Fuel Pumps designation from Saleen as on S351R MRSPs. They came with the Vortech Boost Retard Ignition box and the "Dial-A-Retard" knob. They also all had the FMU running off of Vacumm Boost. The set up was standard fare in the day but complete junk now.

When we just finished re-working and retuning the Mystic S351R, which has a 408 Eagle Forged Stroker Kit in it now, we got rid of a lot of this crap and boy am I glad we did.

In the end, we went with:

Aeromotive 304 lph In-Tank Fuel Pump (#A-11140)
Anderson Big Pump In-Line Fuel Kit (#KITAF-6294)

Replaced all the Fuel Lines front to back with Aero-Quip properly sized units.

High-Flow Saleen/Vortech (Just Use Vortech) Fuel Rails
Siemens/Deka High Impedance 60 lb Fuel Injectors (#MTN-SD60)
Aeromotive Fuel Pressure Regulator (External not rail mounted since Vortech Rails do not have Regulator mount)

MSD 6AL CD Ignition (#MSD-6420)
MSD Universal Ignition Wiring Harness (#MSD-8874)
MSD Blaster TFI Coil (#MSD-8227)
MSD Pro Billet Ready to Run EFI Distributor (#MSD-8451)
MSD Extra Duty Distributor Cap (Black) (#MSD-84083)
Taylor 10.4mm 409 Pro Race Spiro-Wound Spark Plug Wires (Red) (#TAY-79267)

Anderson Power Pipe Vortech Induction Kit (95 - 5.8L) (#AF-0102C)
Anderson Air-Filter and Mass Air

Moates Quarterhorse Computer Tuning Chip (#QH1)
Moates Binary Editor 2010 + EEC Analyzer
Moates EEC Editor Software from Paul Booth EEC4 DEF+DLM (#EEC4 DEF+DLM)

We have a ton more stuff on the car from Snow Boost Methanol Injection, smaller Boost Pulleys, etc., etc. various other fine tunin things.

You have to understand that in the mid-90s, what Saleen put out was all there was. You could not put larger injectors on without drivers, etc. We put the Moates chip in because it gets rid of the stupid FMU and Retard box set-ups. In the end, if all your internals are strong and in great working order, concentrate on the weakpoints of the S351R, which are ignition, fuel and tuning. Well heat can be a probelm too, but sounds like you have that liked already. We put in a Busch Grand National Spec Griffin Dual Pass Aluminum Radiator in the Mystic S351R (ala 99 S351R spec) Cured the heat probelm right there.

Basically the problems on the early cars were they did not have forged internals and running as lean as they were, "Kaploowy". 99s had Forged Internals which in addition to the new edge body style is why people want them. However they too had probems with ignition, fuel and tuning to get the most out. All Saleen S351Rs did.

The good thing is when you get the balance right, the right parts installed and get them tuned for your altitude and location, they are downright awesome. Nothing else like it out there. However without the right guy to work on them and dyno tune them properly, it is very hard to get them running optimally so do not be hard on yourself.

On our re-work we had to send some parts back to the manufacturers becuase they were not in spec to work properly. The perfect balance makes all the difference.

This winter I am doing a major detailed write up on everything we did to the Mystic S351R with part numbers, etc. to get 579 rwHP and 648 rwftlbs out of it at 91 degF and over 6,000 ft altitude with zero detonation or issues. It can be done but the big thing is do NOT cheap out on the parts you out on it to make this work and you have to go with the right tuner with patience to dyno tune it properly.

Hope ome of this write up helps.

Thanks
Rick

87 vert · #30 08-20-2012

Ignition and boost retard were done via the computer in 97 up cars!

Don't ask how I know this! T rex would be where the other Scott stated in front of the well for the spare tire.

ricksaleen · #31 08-20-2012

BTW 99 S351Rs, T-Rex should be mounted on the fuel cell shield between tank and rear axle and you will definitely hear it when you turn the key to accessory before you start it.

ricksaleen · #32 08-20-2012

Thanks Scott;

I knew they did something different on the 97 and up which is why a lot of pre-97 S351R ownes sent the cars back to Saleen for the '97 Saleen Fix but couldn't remember if they did get rid of that box or not. That's for clarifying that up. So they just dumped the Vortech Ignition Retard Box and the "Dial-A-Retard" knob, but there should still be an FMU, etc.

In the end, just Moates Chip it and get rid of that crap!

99S351 · #33 08-21-2012

No, the FMUs were gone after 95. The ECMs handled the timing and fuel starting in 96, no more bandaids. Saleen was learning from warrantying the 94-95 cars. Gradually bigger injectors and fuel pumps were used and the tunes changed. Im gonna have to get mine on a lift and remove that metal tank shield and see if I have a aux inline T Rex pump. When I turn the key, all I hear is the intank pump priming and shutting off. No constant hum of a T Rex. Car runs good though. On the freeway, Id say its at least as strong as my 04 Cobra was when it was stock, maybe faster. I just want the S351 to run as best and as safe as it can.

ricksaleen · #34 08-21-2012

I stand corrected on the FMU. Most of the 351s I have seen have all been 94/95s. 96 were a hodgepodge from Saleen. I had some pictures of what I though were newer S351s but must have labeled them wrong as they still showed FMUs on them.

In the end, we can all agree that the FMU and Retard box were junk. Not saying that the later Saleen's were tuned perfectly either as everyone has stories.

Saleen_S351 · #35 08-21-2012

Quote:

Originally Posted by ricksaleen

All 94-99 S351Rs came with the base Vortech 351 Supercharger kit pieces which included the T-Rex Boost-A-Pump (External) located in front of the fuel tank (between tank and axle) and an inline 255 in the tank (Internal) hence the Dual Fuel Pumps designation from Saleen as on S351R MRSPs. They came with the Vortech Boost Retard Ignition box and the "Dial-A-Retard" knob. They also all had the FMU running off of Vacumm Boost. The set up was standard fare in the day but complete junk now.

When we just finished re-working and retuning the Mystic S351R, which has a 408 Eagle Forged Stroker Kit in it now, we got rid of a lot of this crap and boy am I glad we did.

In the end, we went with:

Aeromotive 304 lph In-Tank Fuel Pump (#A-11140)
Anderson Big Pump In-Line Fuel Kit (#KITAF-6294)

Replaced all the Fuel Lines front to back with Aero-Quip properly sized units.

High-Flow Saleen/Vortech (Just Use Vortech) Fuel Rails
Siemens/Deka High Impedance 60 lb Fuel Injectors (#MTN-SD60)
Aeromotive Fuel Pressure Regulator (External not rail mounted since Vortech Rails do not have Regulator mount)

MSD 6AL CD Ignition (#MSD-6420)
MSD Universal Ignition Wiring Harness (#MSD-8874)
MSD Blaster TFI Coil (#MSD-8227)
MSD Pro Billet Ready to Run EFI Distributor (#MSD-8451)
MSD Extra Duty Distributor Cap (Black) (#MSD-84083)
Taylor 10.4mm 409 Pro Race Spiro-Wound Spark Plug Wires (Red) (#TAY-79267)

Anderson Power Pipe Vortech Induction Kit (95 - 5.8L) (#AF-0102C)
Anderson Air-Filter and Mass Air

Moates Quarterhorse Computer Tuning Chip (#QH1)
Moates Binary Editor 2010 + EEC Analyzer
Moates EEC Editor Software from Paul Booth EEC4 DEF+DLM (#EEC4 DEF+DLM)

We have a ton more stuff on the car from Snow Boost Methanol Injection, smaller Boost Pulleys, etc., etc. various other fine tunin things.

You have to understand that in the mid-90s, what Saleen put out was all there was. You could not put larger injectors on without drivers, etc. We put the Moates chip in because it gets rid of the stupid FMU and Retard box set-ups. In the end, if all your internals are strong and in great working order, concentrate on the weakpoints of the S351R, which are ignition, fuel and tuning. Well heat can be a probelm too, but sounds like you have that liked already. We put in a Busch Grand National Spec Griffin Dual Pass Aluminum Radiator in the Mystic S351R (ala 99 S351R spec) Cured the heat probelm right there.

Basically the problems on the early cars were they did not have forged internals and running as lean as they were, "Kaploowy". 99s had Forged Internals which in addition to the new edge body style is why people want them. However they too had probems with ignition, fuel and tuning to get the most out. All Saleen S351Rs did.

The good thing is when you get the balance right, the right parts installed and get them tuned for your altitude and location, they are downright awesome. Nothing else like it out there. However without the right guy to work on them and dyno tune them properly, it is very hard to get them running optimally so do not be hard on yourself.

On our re-work we had to send some parts back to the manufacturers becuase they were not in spec to work properly. The perfect balance makes all the difference.

This winter I am doing a major detailed write up on everything we did to the Mystic S351R with part numbers, etc. to get 579 rwHP and 648 rwftlbs out of it at 91 degF and over 6,000 ft altitude with zero detonation or issues. It can be done but the big thing is do NOT cheap out on the parts you out on it to make this work and you have to go with the right tuner with patience to dyno tune it properly.

Hope ome of this write up helps.

Thanks
Rick

Rick, this is the best and informative article i've read. If able, please post pictures of your final master piece. I can PM you if you prefer but I think everyone here would like to see what you've done/created.

Jose

ricksaleen · #36 08-22-2012

Will do guys! I just have to find time to do it right. It will be a complete PDF file with detailed write up, pictures, part numbers, dyno graphs, etc. I have it all ready to go, just need time to assemble it.

We are REALLY happy with the set-up now. We changed sensor positions for certain things, a ton of the right equipment and thought went into this rework. We sandblasted slightly rough pulley surfaces, changed idler pulley locations, added an extra pulley roller to help wrap blower belt on the backside of Blower pulley (since a too large pulley before pre-maturely wears out the bearings in the blower housing) and went with a Prototype "Green" Sticky Blower belt for ZERO slippage (I am providing the company the feedback and it should be available on the market soon, yet it looks extremely factory looking other than the ugly green blower belt, but boy does it work boys.

Just be patient with me as I know a lot of people are going to be studying this build up PDF I create for their potential future reworks. It cost a bit to do with the good quality parts and took two years of planning beforehand but boy are we happy with the results. The car is so deadly and fun, I just sold my 2006 Viper SRT-10 Coupe as the rekindled love for the S351R Mystic was too much. It is so additive now, it is the only thing in my mini collection I want to drive now. I would honestly put this car up against most anything out there now. Wow! Wow! Wow!

Thanks
Rick

xmarine97 · #37 08-25-2012

I have one question. I see where you used the Anderson power pipe. Did you have to enlarge the hole or make another hole for the power pipe. Thanks

S351r · #38 08-25-2012

It has to be enlarged

ricksaleen · #39 08-26-2012

Scott is correct! We enlarged the hole for the Powerpipe and then used some thin "conveyor belt" to cover the front hole to keep the dust out and make the area have a real clean look.

Here you go:

And doing all this, look what I found tucked away in the front valence:

ricksaleen · #40 08-26-2012

Here are a few more. As I said a major write up coming as we changed out harmonic balancers, fabricated catch cans, just a ton of stuff:

Yes that is the air intake temp moved from inside the fender to the actual intake:

A little Methanol anyone? All hiden for the right look:

Methanol storage tank (all fabricated):

Had to replace the stock MAS. The new set up with the PowerPipe sucks pretty hard. It did this on the dyno. Ha! Ha!

ricksaleen · #41 08-26-2012

Painted the new MSD box Black and added in the new fabricated Catch Can system from the 08 Saleen Catch Can system. This is pre-prototype "Green Sticky" blower belt:

Need to paint the oil pan as you can see where it was beaten out by the previous owner when the 408 Stroker kit went in. Shows new harmonic balancer, etc. Saleen also beat on the car in a few places underneath to make things fit on the S351s. Picture includes the aluminum rack steering bushings if anyone has not seen those. The G-Load brace was being recoated so I will have to provide updated pictures when it is back on.

Added two little lights to a replacement gauge pod (Green means methnol is injected and red means tank is low) Lower side panel is off as Moates chip was being installed. Picture also shows Saleen SR race pedals. Yes the Mystic car had some interior panels lightly sprayed with faint Mystic. This was 9 years before Ford "over" did it on the Mystichrome Cobras.

Here is the young guy who works the magic on the Saleens here in Colorado. It is worth it for you to send Saleen cars to him here in Colorado, he knows what he is doing. His name is Eddie G with Elite Performance and Tuning here in Highlands Ranch, Colorado. Has an infloor Mustang Dyno with all the latest software and just recertified. Mustang Dyno, Moates, SCT, Diabalo-certified. Also Eddie does all the old speed shop tricks with heads, internals, intakes, etc. himself. He has clients from all over the middle east and all over North America sending engines in crates to him to work on the heads and other internal aspects before returning to them. They build all the Cobra Kit cars for Colorado there, work on everything from modern Saleesn to Shelbys to Ford GTs. Also work on all older muscle cars of all makes and the newer cars from Vipers, to Cameros to SRTs to Subarus, etc. Eddie's Subaru WRX is over 800 HP and is pretty insane. The kid is a perfect mixture of old school and modern tuned engines we need for the S351s anyway. He is one to watch for sure and all at the ripe age of 28. Far as I am concerned Eddie is one of the best out there and anyone considering an upgrade to the S351s should at the least be talking to this kid.

PM me if you need his contact info.

ricksaleen · #42 08-26-2012

BTW Sorry Kenny, I did not mean to hijack your thread. Hope some of the information I provided helps.

Also years ago when my fuel pressure was acting exactly like yours, it was the fuel pressure regulator that took a dump. I would replace that and get it adjusted correctly.

ricksaleen · #43 08-26-2012

Finally before I checkout this Sunday, here are some inside shots:

See the difference in harmonic balancers from Saleen versus new:

A look under those valves covers show the lifter rail sets and ARP Head Bolts:

Those lovely little Titanium Push rods:

We replaced the stock cloth inside the ground effects with steel mesh as in newer Saleens. Boy Saleen went all out on the originals, huh? Ha! Ha!

Snow Boost Stage II HP Methanol Pump was located right beside the convertible lift hydraulic pump (all hidden)

Next year will be one more step to getting it back in original SEMA shape:

Which means all this stuff we took forever to find, will be restored and going back on the car:

Sc-rcode · #44 08-26-2012

Very nice Rick I can't wait to read the whole write up on this thing!

OxfordS281 · #45 02-07-2015

Awesome build!