I drove it to work then tried to start it later in the day, it got me to the end of the parking lot then died. I am also working on a coolant problem, but I don't know it it is related (heater core is leaking). There is coolant, but even so, it should start (engine is cool too). It cranks, runs poorly for a few seconds, then can't keep running and stops, like my firing order is messed up or something. I just changed the oil last week, it is all still there, there is coolant, voltage, etc. I tried disconnecting the battery for several minutes to "reboot the car", but that didn't help.

Any advice? I'm going to replace fuel filter tomorrow, and take it from there, assuming it is fuel related.

 

Is it smoking when it starts dying, and if so, what color?

 

No smoke.

 

I would also suspect a fuel system related problem. Do you have a fuel pressure guage to check for fuel flow at the rail?

This would narow your search.

 

Also check to see if you have a strong spark.

 

Can I check codes for this? I don't have an H pin like my manual said, the only pin on the bottom row is G (bottom left).

I discovered if I start it and not hit the gas it will run for a few seconds then stop, or if I start it with the fuel pump fuse pulled it will do the same. If I start it and hit the gas it will die immediately.

 

to check for codes turn ignition on
use a paper clip to jumper terminals 'A' and 'B' (closest to transmission)
if no troubles you will see only codes 1 and 2
code12 3 times followed by trouble codes
good hunting

 

No codes, just 12 (more than 3 times). Will it just keep doing that if there is no data or am I not being patient enough?

My radiator fan turns on when I short A + B BTW, is that normal?

I also changed the fuel pump relay, seemed like an easy thing to try, that didn't work.

 

Codes are normal. You need to check spark and fuel as suggested. Borrow a fuel pressure guage and tape it to the windshield. Also check spark on at least one plug to confirm spark is working. With spark and fuel it should run, if not something is way off. Any other clues: any mods - other problems recently?

Best of luck,

Pete

 

I bought a fuel pressure guage, it went up to about 17 PSI (guage goes up to 100). My manual says it should be more than 34, so I still have to change that filter I didn't get to today.

I also still need to check spark, nobody wants to help :( It must have spark though, the engine runs for a bit when I move the key to the run position.

 

Congrats, you have found a major boo boo, your engine is fuel starved. Change your filter and see if fuel pressure rises. Also, as an experiment, take the vacuum line off the fuel pressure regulator (and plug the line). This stops the regulator and you will get all the pressure the pump can deliver. If still low fuel pressure, you might have a defective regulator or a worn out fuel pump.
Let us know what you find.

 

I changed filter, no change. I also removed that vacuum line, and put tape over the hole on the regulator. Still won't run. I also changed all the spark plugs, cap and rotor, throttle position sensor, and added some STP gas treatment stuff. Guess my mechanic will have to look at it on Tuesday, I don't think I can change a fuel pump.

 

Being the first real injected vette, you can rest assured if it fires at all, it is not related to any critical system on the ECM... If it were, the ECM would not send fuel so that will narrow the list... If it were my car, I would drop the tank and change the fuel pump... Fuel pressure and flow at pressure are two differnt things... From there I would test the TPS, IACV, MAF and go through the mechanical parts of the throttle system... Beyond that I would move to the ignition module inside the HEI and replace it, the cap and rotor... Look over the plug wires to make sure they are not burned and shorting and then the coil if need be... If it is a fault in the MAF, IACV or the TPS it will be difficult to see so make sure you are careful... If they failed, the ECM would stop the fuel pump relay so if they are bad they will be working improperly not, not working at all... Not sure on the ESC for the 85s but it has to use something and that will be a drag at the very least... Most stuff you can test but I have no idea if an ESC is testable or has to simple be changed...

How many miles on this car and what else has been happening lately with it if anything out of the ordinary??

 

I had the same symptoms and the same pressure reading with a bad fuel pump. There is one more test to nail it down - clamp the return line shut (rubber hose at the end of the larger metal tube going down the front of the engine. Turn the key on 2" - repeat several times to build up pressure. If you get 30-40 psi, then it is the regulator, if no change it is the pump. If you don't see gas in the vacuum line to the regulator, 10 to 1 odds it's the pump.

Pump replacement seems daunting, but it's simple. Remove the gas door and rubber spacer, disconnect fuel and electricals, remove the bolts around the flange and bingo! it's out! Make sure to put on a new strainer with the new pump and you might have to cut a new gasket if it's a Delco replacement. Believe it or not - the pump is easier to replace than the regulator! Go for it! Good luck!

 

69k miles, I've owned it for a year. I just got new tires mounted a few days ago, but that has nothing to do with it.

I discovered my aftermarket keyless entry system went bad last week, I also found some coolant near there so I guess it shorted out. I yanked it out the night before, and was planning on replacing the heater core in a few days. I did drive the car for a day without the keyless entry system installed, stopped and started it maybe 5 times. I tried putting it back in just to see, but that made no change. I would think if something did go wrong with the computer or the security system, I wouldn't have been able to drive the car at all before this problem started.

Do you have to drop the tank to change the fuel pump on an 85? If it is as easy as Hendej says then I will try it, but that proceedure sounds like what I read about for a newer C4.

 

Yes you should be able to change it from the top... I don't usually because checking the straps is a good thing to do as well as the lines... Either way, it is easier to do the work if the tank is out but easier to do the job overall if you go through the top...

I believe your ECM is in the area of your heater core and if it is that means it is an internal ECM... That means it is not water proof so that makes the list of potential problems too... I would still start with the pump... It will not hurt to get a new one in there even if it is not the problem at hand....

 

There are several other posts floating around about fuel pump replacement. I just replied to one of them, check them out to. Replacing the pump is a snap if that's the real culprit.

 

Hey, you don't have to drop the tank to change the pump, you can pull it out the top if you take off the door! Changed the pump, and now it will run, and pressure is about 30 PSI.

I have an other minor problem, I have an error code now, 22, throttle position sensor. That was changed while I was working on it, when I put back the old one the clode clears but the idle is a little rough. Should I make it work with the new one or fix the idle with the old?

Thanks for everyone's help on the fuel pump.

 

If you touched it while working it will need to be reset... I think it is in the tips section on how to do it... Don't want to try and recall the voltage but is something like .5 volts... Make sure you have the right number and it is a breeze with a good voltmeter... If you didn't touch it before, change it... :cool: