wro87

My son (in the military ) will be home soon and while we got his Z out to get it ready have a small problem. 92' 53k miles while driving down the road it would just stop like loss of power had to wait a bit then would fire up and run a bit then quit again got it home.
Changed out the original AC fuel filter and while had it off put a hose on the line and ran it to a bottle. Well it only pump for a few seconds and then quit running IS THIS NORMAL? Left the key on and the pump would not stay running, I thought this odd since I am running it from the fill line on the filter and had no back pressure.

If its the pump which way to go and what one to use? Is it under the filler in the back and how hard to change out?
Thanks gang wro87

Aurora40

It's hard to tell if that is what is happening, but the secondary fuel pump kicks on on cold start, and shuts off once up to temp. If the primary fuel pump has died, this means the car will run until it reaches temp, at which point it will die.

The pump assembly on a C4 is pretty easy, it pulls right out the top along with the filler neck. If that symptom describes what happened to your car, the primary pump may need replacing. Apparently you can replace the pumps only with a 454 Suburban pump for a reasonable cost.

ZR-71

I'm not an expert but here's a few threads on similar probs Good luck

http://forums.corvetteforum.com/c4-z...fuel-pump.html

http://forums.corvetteforum.com/c4-z...m-or-what.html

http://forums.corvetteforum.com/c4-z...fuel-pump.html

http://www.zr1netregistry.com/Old_Proj/old_proj11.htm

wro87

Ok so the way this works now is Would both pumps be on at first and then the secondary shuts off and the primary stays running? When I hooked the hose up tothe filter line it put about 6oz of gas in the bottle then shut off and no more flow. We tried it off and ona couple of times and the pump would not come.
Ok if it appears to be the pumps are they both the same?
I may have located 2 of the Suburban pumps but before I go this route I think I will try out the fuel pressure.
You can start it right up now and drive it a some then it craps out, give it a couple of minutes and it will run again.
It seems with with the help of the forum the primary one has failed and the secondary is running (maybe).

Man when they go it goes REAL quick!!

Man it was running strong just the day before!!

If the gang out there has any more suggestions I will be open to the thoughts.
THANKS GANG
WRO87

glass slipper

Yes, both pumps run when you first start the engine regardless of coolant temperature. If the coolant temperature is below 176°F, both pumps continue to run until coolant temperature reaches 176°F at which point the secondary pump turns off. If the coolant temperature is above 176°F when the engine is started, the secondary pump turns off after two seconds. Based on the info above, you've correctly identified the primary pump as bad.

When you cycle the ignition switch without engaging the starter, the fuel pump runs for two seconds then the ECM shuts off the pump due to no reference signal from the crank position sensor (indicates engine isn't turning over). So what you're seeing is normal.

For future reference, there's a small red wire with a connector on the end close to your battery that looks like somebody forgot to hook it to something. That's the primary fuel pump test connection. With the ignition "OFF", you run a jumper wire from a 12V source to the connector to energize the pump without running the engine to test pressure or to see if the pump will even run. Electric fuel pumps either work or they don't...they don't "slowly" go bad. The electric motor is actually what fails.

Also, from post #8 in this thread linked to in the post from ZR-71 above:
http://forums.corvetteforum.com/c4-z...m-or-what.html

"For test purpose, remove the fuse on the right side end of the instrument panel labeled ENG 2. This fuse is used by the Fuel Pump relay #2. Removing this fuse will disable the FX3 controller, the EBTC module and the Secondary Air Pump. Removing the fuse will prevent the PCM from shutting off the secondary fuel pump when the engine is above 176 F. If the engine now runs normal that would point to a bad primary pump."

I don't know if you read through the linked threads, but the above is probably the easiest test in the world to check for a bad primary fuel pump plus it can get you home if you're far away. Just keep in mind you'll no longer have FX-3, ASR, ABS, or the AIR pump. Be more aware when driving without ASR/ABS, the nannies won't be there to save you.

wro87

Well looks like I will be pulling the pumps OUT but really don't look that hard! ). But still I can't believe that both pumps are the same and they both go thru the same delivery line.
Hell my C-4 with the Modified Engine can get enough fuel and pressure running the stock pump (165MPH on the dyno but was running a little lean until we bumped the fuel pressure up to 50psi).
Well one of those things! Now to get a couple of pumps tomorrow anybody out there as to which one is the best that is not listed on the links above?

Thanks Gang
wro87

erikszr1

HI im having similar problems.....at any point after 176 F do both pumps run together? my car developes a miss like symtom at about 176 F w power key on....hmmmm.. ive done plugs, wires and coils so far... ok thanks in advance

glass slipper

Both pumps will run after 176°F during heavy acceleration when fuel demand gets to a certain point as calculated by the ECM. Based on your symptoms, looks like time to check the primary pump. Pull the "ENG 2" fuse and see if your miss goes away. If it does, you know the primary pump isn't pulling its weight and time to get a new one.

erikszr1

Thank you very much! im going out to try it right now..

wro87

So both of the pumps are the same type?

And I will need to replace BOTH CORRECT??

Thanks Gang wro87

cadillac531

If you do the test glass slipper suggested (pulling the fuse), and the car runs fine, you would only need to replace the primary pump...it's a good idea to do both while you are there, but you only HAVE TO do the primary if you wanted.

As for both pumps being the same, I think they are, but someone else here may know different.

wro87

OK Gang thanks for all the input!!!
So I called Autozone and they have 2 different pumps
E3270 80-90psi
E3240 65-95psi listed for ZR1

Both of them are $90 bucks and they only handle 1 of them but I can drive over to another town (both about 15miles away and pick up the other one). Now which one to go for ??? HMMMMM!

I also Called my Dealer and they have the complete Assmbly for $300 bucks, but will be a day to get it. I think when i get home later i will go ahead and pull it out and see if any water(rust) issues. Have not had any problems with the level sender unit but never know.

Any more suggestions will be well listened too
WRO87

guinnessdood

Bill...read the three articles below and heed everything. Be VERY careful when taking the unit out and installing it in the tank...you can really throw the fuel level calibration out of whack if you're not extra careful. ZR-71 is right on with his links too...read and heed...

http://www.zr1netregistry.com/Old_Proj/old_proj11.htm
http://www.zr1netregistry.com/fuelpump.htm
http://home.comcast.net/~zrjuan/sender.html

wro87

Hay GANG Thanks for the insite/help. Well I have read the links and printed out some of the destructions for reference. Also later today I also found a complete GM unit on flebay for $270 including shipping and Delphi for $200. The way I look at it now is if I 'm going to spend 180 bucks for 2 pumps might as well put the whole thing in will check things out when I can get up to our shop and will let all know how it turns out.

Thanks gang
wro87

wro87

Well gang was able to pick up a complete assembly (ebay). Delphi part gm box assembled in USA in 08' according to the tag with GM #'s for the delivered price of $162.00. With all the help from U it took less than 10 mins to pull the old ones out (had to cut some wires aftermarket fuel pump kill swiitch had been installled), and only about another day (dropped a bolt somewhere to late at night to get one) really about another 10mins to install.

BACK ON THE ROAD AGAIN

Thanks wro87

Paul Workman

Congratz on finding and fixing your fuel pump issue!

Funny (now) story...

My secondary pump failed. When I pulled the assembly out, there was some read lint on the filters. (Oh! You DID change the filters, right?). While the assembly was out of the tank, a took a look around the inside of the tank and found a red shop rag floating in the fuel!!I recon that explained the red lint.

I don't know if that had anything to do with the pump failure, but it sure might have been the reason the fuel level reading was so friggin erratic!!

P.

wro87

When the new assembly came in it had all the filters (the original ones where just a little discolored)and everything else took less than 10 mins. to drop it in and then just bolted it down and plugged it in. WHAM BAMM!!
Then told the wife to take it out and try it! Well she got back and said it ran fine she got it up to 92MPH oboy! Asked how well did it run when you turned the GO FAST KEY ON and she said whats that. Well pointed it out to her again and off she went!

Thanks gang for all the info
WRO87