Question : 3100 Will Not Fire

[Braddock]

Forgive me if this is asked every other day, but I'm having quite the time with this one.

I am looking at buying 1994 Pontiac Grand Am for 200 dollars that will not start. I want to get a better picture of what I might be committing to though.

We have spark, we have fuel. The plugs look good. The air filter is clean.

Spark seems consistent on all wires. Checked compression. ~120 psi on the cylinders I had a chance to check.

The engine just refuses to start. Any ideas?

Thank you in advance!

[neophile_17]

How did you check for fuel? 120psi seems low to me but I'm not as familiar with that motor specifically.

[Heartbeat1991]

If you have spark and fuel, you need to check for vacuum leaks. It would have to be a big one to keep it from firing. Could be timing. If the chain is broke, it won't fire. Or it may have jumped timing. Also make sure the ignition wires are routed correctly.

[Braddock]

If you have spark and fuel, you need to check for vacuum leaks. It would have to be a big one to keep it from firing. Could be timing. If the chain is broke, it won't fire. Or it may have jumped timing. Also make sure the ignition wires are routed correctly.

What's the quickest way to determine if the chain has jumped or the timing is off? I could not find timing marks on this motor when I put my light on it.

[Heartbeat1991]

I'm not sure of the easiest way. Pulling off the valve cover would get you a good idea. But not very precise. Compression check you already did. That could point to a timing problem, but You'd have to check them all. The only sure way is to pull the timing cover, as far as I know. But it's not likely to have jumped. All the ones I have seen with a timing problem had a broken chain.

[Purple pit]

Bad crank sensor?

[Heartbeat1991]

Bad crank sensor?

That's possible, But I am pretty sure that would result in no spark at all.

[neophile_17]

My thoughts:
You wouldn't get good compression on all (or even 1/2) of the cylinders with a broken chain.
If you have fuel at the rail but the injector fuse is blown or the wiring is faulty you might not have fuel in the engine. Your injectors might also be clogged. Try pouring a small (like teaspoon) amount of fuel in the intake.
Your timing could be off or wired wrong but if you verified spark it's unlikely that your crank sensor is completely dead.
Do you have a check engine light. Is the bulb OK? It should come on when the key is in run before you try to crank it.

Sorry if any of this seems stupid, but we don't have a ton of information.

Sam

[Heartbeat1991]

My thoughts:
You wouldn't get good compression on all (or even 1/2) of the cylinders with a broken chain.
If you have fuel at the rail but the injector fuse is blown or the wiring is faulty you might not have fuel in the engine. Your injectors might also be clogged. Try pouring a small (like teaspoon) amount of fuel in the intake.
Your timing could be off or wired wrong but if you verified spark it's unlikely that your crank sensor is completely dead.
Do you have a check engine light. Is the bulb OK? It should come on when the key is in run before you try to crank it.

Sorry if any of this seems stupid, but we don't have a ton of information.

Sam

I agree with Sam. We are shooting in the dark, here.

If you're sure there is fuel and spark, it makes no sense that there isn't fire, unless the aren't present at the same time. :-)

I would skip the pouring fuel into the intake and just use some starting fluid. Spray a couple short bursts into the intake and see if you get anything.

[Braddock]

My thoughts:
You wouldn't get good compression on all (or even 1/2) of the cylinders with a broken chain.
If you have fuel at the rail but the injector fuse is blown or the wiring is faulty you might not have fuel in the engine. Your injectors might also be clogged. Try pouring a small (like teaspoon) amount of fuel in the intake.
Your timing could be off or wired wrong but if you verified spark it's unlikely that your crank sensor is completely dead.
Do you have a check engine light. Is the bulb OK? It should come on when the key is in run before you try to crank it.

Sorry if any of this seems stupid, but we don't have a ton of information.

Sam

Thank you.

Yes, I have fuel at the rail. I have not had a chance to test PSI as I do not have a fuel pressure tester and money is tight. I may get one on Friday if I must. I have tried spraying about 3 seconds worth of ether into the intake and it did not bite. Perhaps I need to use more fluid.

I have a healthy and consistent spark. tested with the plugs currently in the car.

I have a check engine light. It comes on when I put the key into the run position and stays on after the light test is finished.My OBD 1 reader does not seem able to pull anything form it. However, my reader does not like pulling OBD 1 codes from working cars either. Can the paper clip trick be used on this model?

[Heartbeat1991]

It may. Some 1994 have OBD 1.5. I would give it a try. I think that car is OBD 1, but don't hold me to it for sure.

Fuel at the rail does not mean the injectors are spraying fuel into the engine. But the ether should have gotten it to at least sputter.

[Braddock]

I just got the chance to do another compression test in the daylight with enough time to do it right.

Firewall Side
1: 195 PSI
3: 195 PSI
5: 195 PSI

Front Side
2: 110 PSI
4: 155 PSI
6: 155 PSI

I tested and retested cylinder 2. Couldn't get any higher than 110 PSI.

[Braddock]

It may. Some 1994 have OBD 1.5. I would give it a try. I think that car is OBD 1, but don't hold me to it for sure.

Yeah, its 1.5. I cant paper clip it and my OBD 1 & 2 reader wont read it either.

[3400-95-Modified]

Compression like that will not result in a no fire... You have an issue with fuel making it to the cylinder. This isn't like a carb engine where you can just say YES the pump is putting fuel in the bowl and that's good to go... Yeah you may have both fuel and pressure at the rail but the injectors are not opening and closing due to a short or straight up no connection so no fuel makes it in.

Spray some starting fluid into the TB when trying to crank... If it catches and attempts to start then your injectors/or wiring to them is definitely to blame.

Oh and the check engine light I believe will stay on until the car starts... regardless if there is a code or not. OBDI.5 or non prom OBDI computers will still work with OBDI readers. I used to use one on my 95 Beretta.

[Braddock]

I did use starter fluid. It didn't even sputter.

I've replaced the plugs and wires and the spark is blue and every cylinder is getting a spark.

My reader will not read it, and the paper clip doesn't work either.