98 Astro wont start

[pkdb]

One morning it just wouldn't start, smells "flooded". When cranking over it seems like it wants to fire up, but doesn't, have not pulled a plug yet, but smell raw gas from exaust pipe, and I think in the engine compartment (never smelled raw gas before). I have spark, checked the Cam sensor, coil,IAC,MAF,Air temp, all in spec. Crank pos sensor was out of spec-replaced.

Fuel press. is 62 psi+. But will "bleed off" to 50psi in about 15-20 min or so, down to 10 psi over night.

My thought is that fuel is somehow leaking into the engine (fuel pres reg?) without being controlled. Is that possible? If so how?

Any ideas what to check next, before going to the dealer?

Thanks, Paul

[MT-2500]

Originally Posted by pkdb

One morning it just wouldn't start, smells "flooded". When cranking over it seems like it wants to fire up, but doesn't, have not pulled a plug yet, but smell raw gas from exaust pipe, and I think in the engine compartment (never smelled raw gas before). I have spark, checked the Cam sensor, coil,IAC,MAF,Air temp, all in spec. Crank pos sensor was out of spec-replaced.

Fuel press. is 62 psi+. But will "bleed off" to 50psi in about 15-20 min or so, down to 10 psi over night.

My thought is that fuel is somehow leaking into the engine (fuel pres reg?) without being controlled. Is that possible? If so how?

Any ideas what to check next, before going to the dealer?

Thanks, Paul

Welcome to AF.
A slow leak down like that is normal.
Have you got spark to more than one spark plug?

[pkdb]

Hmmm. Only checked one, I'll check the others.

Thanks, Paul.

[pkdb]

Ok, I finaly got back to my Astro. With a fully charged batt, I was able to get it to start, very rough and bounced around alot while starting, but did. So it ldles fine, but step on the accelerator and as the rpms rise, it "misses" like crazy, almost stalls. Let up and it idles fine again. If you press it very, very slow, the rpm will rise will only a little "missing". stomp on it and it nearly stalls (like an old carb engine) then rpms rise roughly. The only sensor I found that tested out of spec was the one on the front underneath crankshaft-replaced-no difference.

Could it be starving for gas, fuel filter? any other ideas?

Thanks, Paul

[MT-2500]

Fuel filter is a good start.
Plugs and wires and dist cap to.
If running that bad you should have some codes.
Any check engine lights on?
Post back any codes.
And always run a fuel pressure test on them.

Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.
MT

[pkdb]

There are no codes posting, hard to believe I know, I scanned it a number of times, even while accelerating (when it misses most). Cap, rotor and wires aren't THAT old and look good, but I know that they can still have issues. I have 63psi key on engine off. I'll do a running pressure check and keep the process of elimination going.

Thanks,
Paul

[pkdb]

I replaced the fuel filter, with no improvments.
When the key is turned on the pressure reads 62psi for a few seconds, then drops to about 53psi. when the pump stops.

Running pressure in driveway is at 52-53psi. and it idles smoothly.
When I step on the gas, the pressure will jump to 60 as the engine revs, but then it "misses" really bad and pressure drops. (I couldn't tell if the pres. was dropping because of the missing, or missing because of the drop, it seemed simultanious, if they are even related).

The return line is all metal so I havent blocked it off yet to get that pressure reading.

Still no codes, I tried reading them numerous times, even while I was on the accelerator(missing) and no codes, and nothing in the other areas the scanner reads.???

Could it be timing? maybe not advancing? since it idles smooth??? Or fuel?

[CD Smalley]

I'm betting on a leaking injector since your bleed off went all the way to 10psi over night. I could be wrong, but given you have one of the multi point injection style of systems vs. TBI, that just shouldn't happen.

Are you seeing one plug look wetter than the rest??

[pkdb]

Hmmmm. I'll have to check them again now that it's sort of running. Thanks.

[old_master]

Could even be the check valve in the pump leaking. The only way to find out for sure what's causing the leak, requires two special tools. One is temporarily installed in place of the fuel filter, the other is installed in the fuel return line. Each tool has a shutoff valve and a fuel pressure service port for the pressure gauge.