richz2.8

To start, I have an 85 sport coupe, the motor is not original. I was told it came from a 94 firebird. Come to find out it is not the 2.8 but the 3.4. Found this out when I bought an injector, and had to go back because it didn't fit right, or look like the others. I bought a new starter, new fuel filter. I crank it and it acts like it wants to start but doesn't. Fuel pressure is good but goes down after a few seconds. Would love to fix it so i can stop having my wife drop me off and pick me up from work.

richz2.8

Also, temp sensor on the newer radiator has no wire to connect to it, is this wire supposed to be there on an 85?

Project: 85 2.8 bird

some Q's for ya:

any codes? I still have my 85 Firebird service manual.

fuel leak? what pressure is it getting up to, and how fast is it leaking down?

obigatry: everything hooked back up correctly?

ex-x-fire

Whats the fuel pressure? And it is supposted to hold pressure, you've got a bleed down somewhere.

fasteddi

iTrader: (2)

Agree with that!!

Maverick had a really good outline on how to do a leakdown test for the fuel system somewhere. Im short on time right now or id search and find it for you. From what I remember of it, it was very detailed and easy to follow for anyone to perform. So if you have questions about it i'd search for that specific thread. You'll know it when you find it.

My opinion though which is just a opinion as I by no means am I qualified to tell you whats wrong with it.

If it bleeds off the fuel that fast you either have one of a few problems. The fuel pump is shot and cannot sustain the correct pressure and flow, one or more injectors is leaking terribly, faulty FPR, or the fuel is literly leaking into the tank itself off the in tank assembly. I personally had the issue where the fuel pump was leaking into the tank. I though It was a bad fuel pump and then relized that It wasent the fuel pump at all after I got a new walbro one. Just a few things to think of. Heres the reason you need to do a leak/bleed down test to make sure you prove the problem before you change the questionable parts.

richz2.8

would these things cause it not to start?

richz2.8

fuel pressure goes above 42psi then in a few seconds goes back down to 0.

fasteddi

iTrader: (2)

Helll ya man thers no way that cars gonna start with it dropping like that.

Do you know or understand how to preform a leak down test?? Ill try and find mav's write up because hes much better and more knowledgable then I am in that area. Let alone I dont want to confues you.

richz2.8

no i don't, I will try to look it up though.

fasteddi

iTrader: (2)

Its irritating me that I can not find that specific thread but heres a little of what mav said in a recent thread.

"1. KOEO, note fuel pressure. Between 37-47 PSI and holding for 20 minutes, good. You already know it's not, so it's on to step 2.
2. Use a clamp of some sort or locking pliers with a folded rag between the jaws to clamp off the fuel pressure hose in the engine compartment after fuel pump shuts off. Pressure holding means either the check valve in the fuel pump is bad or there is a leak between the tank and the engine. Pressure not holding, step 3.
3. Remove clamp from pressure hose and put it on the return hose. Cycle pump again. Pressure holding means leaking FPR. Not holding, step 4.
4. Cycle pump again after finding second clamp for pressure hose. Put clamp on pressure hose LEAVING THE CLAMP ON THE RETURN HOSE. Pressure still drops, leaking injectors. And yes, I've had injectors leak without a noticeable drip (the set of 3.4 injectors I had)."

Explains it better then I would...lol

richz2.8

no codes or check engine light

Project: 85 2.8 bird

also check for pin holes in the fuel lines, i found some when i put the 3800 in, had to trim the metal lines back some in the engine bay

richz2.8

I would hate to put a clamp on anything rubber under the hood, may break. Would loosening a nut here or there in the line, maybe one at a time, let me know if there is fuel going where it shouldn't.

ex-x-fire

First, pull the vacuum hose that goes to the fuel press. regulator, have someone cycle the key & watch for fuel to leak.

fasteddi

iTrader: (2)

Ive done it before and it works fine as long as you dont go crazy with clamping force. They actually make clampons that are made for this which is what I used when I had issues.

richz2.8

Well, changed the fuel pump today, that was a job. Tank was half full and didn't have a way to siphon it. Put it all back together and still no start, but to be fair some of the vacuum lines are not hooked up and the air intake gasket is missing some chunks from replacing the injector that was the wrong size. Would this still make it not start?

ex-x-fire

Why did you change the pump? The original one was building pressure.

richz2.8

it went up to 42 psi then immediately dropped to zero.
I was told if the pressure doesnt hold then the car wouldn't start.

richz2.8

Well, I put an ohm reader to the injectors and 3 were around 5 ohms, one at 10, and 2 at twelve. I replaced the 4 and kept the two that were reading 12 ohms. I hope this fixes it. There is a plug that looks like an injector plug behind the fuel rail, a thin fuel line comes out of the rail and runs to it. What is this and can it go bad?

ex-x-fire

Pinch off the return fuel line & cycle the key. Does it hold pressure?
Try to take a picture of the inj plug that your talking about. I don't think those years had cold start injectors.

richz2.8

its holding pressure. its not an injector plug, just looks like one, similar to the coolant sensor plug too. its under the distributor, can't get a good pic.

Project: 85 2.8 bird

cold start injector

richz2.8

is this something that would cause my problems? Should it read 12 ohms also?

richz2.8

The motor came from a 94 firebird and is a 3.4.

fasteddi

iTrader: (2)

the intake must be off a 2.8L because im unaware that any 3.1l or 3.4l came with cold start injectors.

If that cold start injector is leaking badly it could cause your loss in fuel pressure.

Maverick H1L

iTrader: (8)

It doesn't matter what year the base engine (long block) is. If it's using the top end off of the 85, it has a CSI. That plug by the dizzy needs to be plugged in. The calibration for the CSI cars is different from the later ones due to the fact that the CSI only provides extra fuel to the startup and some of the warmup (until the coolant switch reaches a temp of 100*). There really isn't an easy way to plug off the CSI because it has a rather large fitting in the fuel rail. And cold starts WILL be affected without changing the cold calibrations.

ANY fuel injector having a resistance reading below 11.8 ohms (generally, can go down to 10.4, but no lower) is garbage. You already replaced them, but for further reference.

FIX THE INTAKE GASKETS. And check for broken/disconnected vac lines and hoses... These engines REALLY hate vacuum leaks.

richz2.8

New development, The engine will run as long as I am spraying carb cleaner in it. Once I stop the motor backfires through the intake and stops. I already replaced the injectors, fuel pump, and fuel filter- what other fuel issue could I have.

Project: 85 2.8 bird

fuel pressure regulator?

richz2.8

regulator is good.

fasteddi

iTrader: (2)

Timing issues?? IDK

Maverick H1L

iTrader: (8)

Is the SES light on when you turn the key? If not, could be either a dead bulb or no power to ECM (ignition module works independent of the ECM until engine speed reaches 400 RPM). Do you hear the fuel pump run when you turn the key on, or when the engine has been cranking for a bit (oil pressure switch)?

Disconnect the fuel injector harness with the key on (the connector in the FRONT), and probe the engine harness connector's pink wires with either your meter or a test light. Should have power on both pink wires. If not, either there is a wire problem or the INJ fuses in the dash are blown.

Passing both, get out the test light again and hook it to a POWER source (battery or alternator gets the alligator clip instead of a ground like usual). Put the probe in either the green wire or the blue wire on the engine harness side of the injector connector. Crank the engine and the light should flash (this does not work with a DMM!). If not, check your engine grounds on the backs of the cylinder heads first to make sure they're tight and clean.

Other than the above, there could be a problem between the ignition module and the ECM where the ECM doesn't know the engine is running.

richz2.8

I will test the connections tomorrow and post results