new crossfire owners who want thier car to run better read this!!

[hotshotzny]

its been said before and will be said again im sure but i cant stress it enough to anyone who buys an 82 or 84 vette.... REPLACE THAT STOCK FUEL PUMP WITH AN 85!! it took me a few people telling me when i had my 82 to give it a shot and boy did it work!it was the first thing i did when i got my 84... unfortunately the one i put in my 84 last year was obviously no better than the stock pump because i had nothing but issues this season with the car running bad.. and i figured it had to be something else so i replaced a bunch of other stuff... then as i neared the end of my rope i went out and got a new bosch fuel pump from advance and within half an hour my car was running like new! if you are going to throw money at anything make it that first off and see what it does.. you wont be disapointed

 

[MN-Brent]

The preferred replacement is the AC Delco EP241 for this mod. Others have proven not to last the test of time.

You an also take it a step further and mod your regulator and install a fuel pressure gauge and bump your fuel pressure between 13 and 14PSIG.

When I did mine, it was a noticable improvement in idle quality and throttle response.

 

[nelson84]

You have to mod the fuel pressure regulator or it will only produce crossfire pressure numbers.

 

[badglas]

Fuel Pump Mod

Be careful with this mod, the regulator, even when new was not designed to deal with the the added pressure of an 85 pump. The stock AC Delco pump and a properly tuned system will run as well or better than the mods you suggest. The trick is in the tuning.

Ron Kane
Benchmark Corvette Service
Bloomington Gold Restoration Workshop Senior Instructor

 

[mmcolor]

1984 correct fuel pressure

Hi Ron. I want to check my 1984 crossfire fuel pressure when I put in the new fuel filter. What pressure should it have on a stock 1984 system. Also where do I check it if not at the filter itself. (I don,t remember seeing any testing valve's as on newer systems) Thanx

Be careful with this mod, the regulator, even when new was not designed to deal with the the added pressure of an 85 pump. The stock AC Delco pump and a properly tuned system will run as well or better than the mods you suggest. The trick is in the tuning.

Ron Kane
Benchmark Corvette Service
Bloomington Gold Restoration Workshop Senior Instructor

 

[Buccaneer]

Hi Ron. I want to check my 1984 crossfire fuel pressure when I put in the new fuel filter. What pressure should it have on a stock 1984 system. Also where do I check it if not at the filter itself. (I don,t remember seeing any testing valve's as on newer systems) Thanx

GM says that 9-13psi works fine, I beg to differ with that. 13 is marginal at best with an old pump. If your pump can handle it, set it to 14-15 and you'll feel the difference. If you beleive GM, set it to 9 and go blast the car, then set it to 14 and see what happens.

The pressure can be measured in-between the TBs, there are ready made 82 and 84 devices for the crossfire out there.

If your TBs are old, I would throw-in a rebuild kit which has two new bladders in it, one for the regulated side and the other for the compensator and raise the FP. I run 26-28psi on a stock regulator with 90# injectors on my 383 CFI motor with no issues and have been doing it for a long time now. Do not do this with stock injectors and ECM, your motor will not run properly.

 

[VIN_#_00521__Z-51_C4]

Be careful with this mod, the regulator, even when new was not designed to deal with the the added pressure of an 85 pump. The stock AC Delco pump and a properly tuned system will run as well or better than the mods you suggest. The trick is in the tuning.

Ron Kane
Benchmark Corvette Service
Bloomington Gold Restoration Workshop Senior Instructor

I agree with Ron ... I have a 84 CFI ( Still has the stock pump ) and both TBIs are still running without problems, The stock pump seems to be in great shape... I had a 44k( BG product ) 3-step cleaning on the car and I think it really helped improve drivability and performance I haven't had any issues with the fuel yet( may change out the fuel Filter soon, Im not messing with the CFI because its still running good, and it's not broke yet ) It's how the system is tuned and I had a So Cal corvette Guy (from Coast Corvettes ) tune this prior to me buying it - - - - The trick is in the tuning

 

[reddogg]

recently purchased 1982

I was just reading all these replies about fuel pumps. I am leaning towards changing mine. I recently purchased my 1982 and love it, but it does run rough, will the 85 fuel pump help and is there anything I should know before I jump into this project? I would really appreciate all input. Thanks, Reddogg..:confused

 

[badglas]

Fuel pump question

The symptoms you describe are classic for these cars. They are prone to blowing the plenum gasket, which allows air in without passing the throttle plates. This creates a lean condition causing rough idle, as well as the TBI units to become out of synch. I reccommend that you rebuild both throttlr body units, replace the plenum gasket, the fuel filter, and the pump if it is in question. I do not reccommend the higher pressure pump. If you require further assistance, please feel free to contact me. I taught a class on this procedure for several years at the Bloomington Gold Restoration Workshops.

Ron Kane
Benchmark Corvette Service
www.benchmarkcorvetteservice.com

 

[Buccaneer]

They are prone to blowing the plenum gasket, which allows air in without passing the throttle plates. This creates a lean condition causing rough idle, as well as the TBI units to become out of synch.

Curious as to how the lean condition or top plate gasket casues the TBs to become out of sync?

 

[badglas]

TB Synch

As I stated, a blown plenum gasket would allow air into the engine that is not going across the throttle plates. This would cause the TB units to try to compensate. If the air leak is on one side and not the other, this lean condition will cause the TB's to operate out of sync. Replacing the gasket will solve the problem. If the gasket is blown, it's a good idea to check the synch after the repair is made. Chances are it will need to be adjusted. These units operate very well if there are no vaccuum leaks and the synchronization is checked and adjusted every 2-3 years. They operate fairly well if they are never touched. I've seen these cars with 100,000+ miles that have never been touched that run good. If they are regularly adjusted they will perform much better with less problems.

Ron Kane
Benchmark Corvette Service

 

[Buccaneer]

As I stated, a blown plenum gasket would allow air into the engine that is not going across the throttle plates. This would cause the TB units to try to compensate. If the air leak is on one side and not the other, this lean condition will cause the TB's to operate out of sync.

I beg to differ... but there is no way that they can go "out of sync" as you have stated. They are not electically driven and so being mechanically linked together they would have to be adjusted incorrectly to go out of sync no matter how big the leak (vacuum leak) you have. Will they try and drive to various positions (IACs), yes because the ECM is getting inaccurate input from the O2 sensor and IACs are tying to compensate because of the leak (new air introduced) that is not being metered properly, but the TBs are still not out of sync and MUST turn together unless the throttle blade shafts are badly worn and there will be a difference in initial movement between the front and back TB. That would be an out of sync condition and require balancing to get the plates to be sync'ed.

Will the motor run horrible with a huge leak...You bet. It doesn't matter which side the leak is on the top plate, the TBs will still travel together to try and keep the motor running and at idle the IACs will be going crazy to keep the correct idle.

 

[Curious George]

I bet to differ... but there is no way that they can go "out of sync" as you have stated. They are not electically driven and so being mechanically linked together they would have to be adjusted incorrectly to go out of sync no matter how big the leak (vacuum leak) you have. Will they try and drive to various positions, yes because the ECM is getting inaccurate input from the O2 sensor and IACs because of the leak (new air introduced) that is not being metered properly, but the TBs are still not out of sync and MUST turn together unless the throttle blade shafts are badly worn and there will be a difference in initial movement between the front and back TB. That would be an out of sync condition and require balancing to get the plates to be sync'ed.

Will the motor run horrible with a huge leak...You bet. It doesn't matter which side the leak is on the top plate, the TBs will still travel together to try and keep the motor running and at idle the IACs will be going crazy to keep the correct idle.

Well, this is an interesting thread... The TB plates are mechanically linked, there are two fuel injectors, can each injector compensate for different conditions? I don't have a CF motor, but I thought both injectors fired together (aka batch fire), is this not correct? If this si the case how can the injectors / TB become out of sync? Perhaps it is symantecs, and the proper words were not used to describe the issues.

CG

 

[Buccaneer]

Well, this is an interesting thread... The TB plates are mechanically linked, there are two fuel injectors, can each injector compensate for different conditions? I don't have a CF motor, but I thought both injectors fired together (aka batch fire), is this not correct? If this si the case how can the injectors / TB become out of sync? Perhaps it is symantecs, and the proper words were not used to describe the issues.

CG

You absolutely correct and maybe his choice of words were not conveying what he really meant. The injectors fire together all the time along with the plate movement. I'm not trying to bash anyone, just want people to get the correct info vs misinformation, God knows there's enough of that in the CF world. On another note, if the TB shafts are worn that bad, no matter how well you try and balance the TBs they will go out of balance (mechanical sync) as soon as the shafts are moved. I'm jus sayin'...

 

[badglas]

TB Synch

You are correct, a vaccuum leak cannot cause the TB's to become mechanically out of sync. The mechanical setting is just to give a base for the IAC's to work from. The irratic IAC fluctuations are the out of sync I implied. Sorry if my symantics caused confusion. Just to be clear: I believe checking TB sync should be checked as part of routine maintenance. It is the key to keeping these cars purring.

Ron

 

[reddogg]

I have a '88 Monte Carlo SS with a TB or some kind of computer driven carberator that was impossible to rebuild. so I bought a new one, are the CF TBs easier to rebuild or do I need a few special tools? Thanks guys, you all have been a great help.