Malibu won't start :(

[Rootie524]

Ok here's the back story to hopefully aid in finding the problem.

I have a completely rebuilt 3400 in my malibu. I put it all back together and started it up for the first time. It ran fine. I ran it for about 20-30 seconds then shut her off because I heard a vacuum leak (i forgot the vacuum nipple on the UIM). When I got out of the car I looked under it to see about 4 qts of oil on the ground. After further investigation it was coming from where the engine and trans meet. First thought was rear main seal. So i got pissed off and didnt work on it for awhile.

A week went by and I needed to get it out of my garage. So I was going to start it quick and just back it up (yes, even with a huge oil leak..i didn't care at the time). So when i went to start it it would just crank and would not fire up. I found this odd because it started fine before. So anyway..i later preceded to tear the engine out to fix the rear main seal.

After taking it out i discovered that the rear main seal was fine and the jack ass at the machine shop neglected to replaced the oil galley plug he took out when he was freshening up the block. so i plugged it up the way it should be and put the engine back in yet again. I got it all back together and now it's doing the same thing as before. cranks but won't start. and like a said the very first time it started with minimal effort.

Im thinking fuel or spark would be the obvious thing but it could also be a sensor.

I replaced the cam sensor located under the PS pump and the crank sensor behind the harmonic balancer. Now, I replaced them with brand new 3100 parts and not 3400 parts. This is a 3400 but I figured 3100 and 3400 sensors for the most part are interchangeable. Am i wrong in thinking that. is that whats preventing it from firing up?

i checked all my fuses they all are ok. fuel pump makes noise. scrader valve blows out gas when the valve is depressed. ill be performing a compression test later this week.

let me know what you guys think. thanks in advance for any input!

[Jonpro03]

The sensors should be interchangeable. Did you remember the CKP sensor on the back of the block?

[Rootie524]

Yep it's in there all hooked up. That's the one where the wire goes from the sensor to the icm.

[Jonpro03]

Can you pull a plug, ground it, and see if it sparks during crank?

[Rootie524]

ill be testing that later. but for now lets just say it produces a spark, what else could be the problem?

[pocket-rocket]

Crank it before you pull that plug to check for spark. While it's out, smell it/look at it for raw fuel. If you have both, the injectors are doing their thing. If they are dry as a bone, your injectors are just hanging out in the fuel rail plugging things up. That really sucks about the galley plug...

[Schmieder]

I do believe the PCM primes the fuel pump and then refuses to pump further until the Oil Pressure Sensor detects oil pressure which indicates a successful start up.

If the PCM can not detect oil pressure it will shut off the fuel pump. I would try cycling the key on/off with out cranking to rebuild fuel pressure and see if you can get it to run another few seconds. But when the Oil Press sensor fails to give a reading (cause your oil dropped out of the engine) it will not turn on pump and your engine will run until the fuel pressure is gone, roughly a dozen or so seconds.

That's my first guess. Hope you fix the oil leak, or oil gusher....lol

[Rootie524]

that makes sense. but there should be oil pressure now. but because of the first time is still thinks it doesnt have pressure? even though it should be picking it up now? i have my code reader today ill see what all it says..maybe a code needs to be deleted or something. i also have a spare PCM i might try tossing in.

its odd though because i tried what you said already. i primed the fuel pump many times before trying to start it and it wouldnt pick up at all. just cranking.

[Schmieder]

that makes sense. but there should be oil pressure now. but because of the first time is still thinks it doesnt have pressure? even though it should be picking it up now? i have my code reader today ill see what all it says..maybe a code needs to be deleted or something. i also have a spare PCM i might try tossing in.

its odd though because i tried what you said already. i primed the fuel pump many times before trying to start it and it wouldnt pick up at all. just cranking.

In that case there may be more to this. If it isn't even trying to fire over I would suspect no spark first. Because fuel issues often, but not always, backfire or sputter somewhat. Did you check for spark yet?

It doesn't take much oil pressure at all to allow the pump to run. So for that to halt the fuel pump it would have to be a zero pressure situation, like it is sitting still. A safety feature in case the car wrecks and the pump doesn't realize the engine stopped, pushing more fuel from a potentially ruptured fuel line.

Not sure what to check beyond spark atm. Maybe someone else will chime in

[pocket-rocket]

Robert explained to me that the OPSU portion of the fuel pump circuit is just to keep the fuel pump running in the event the PCM doesn't supply power to the pump anymore for some reason. Also, I believe that the PCM would be aware if the engine stopped and would stop sending power to the fuel pump. I doubt that it's as simple as deleting a code. I've never heard of a car not running because of a trouble code. Codes are there to help aid you in diagnosing a problem, not keeping an engine from running. The first time running with low pressure from the massive leak would not cause the PCM not to want to run the pump for some odd reason, either. If it were the fuel pump not kicking back in after the initial prime, it would still at least make an attempt to fire over from the initial prime, anyways. Personally I would first pull a boot and check for spark. Then pull a plug and look/smell for fuel, then if there was no fuel, I would toss a fuel pressure tester on the schrader valve and check the fuel pressure. I wouldn't run a compression test right away if it sounds normal while cranking. Although you may as well while you have the plug out. I worked on a Monte last summer that would stall out and not fire after running for a while. I tossed my fuel pressure gauge on it and when I went to release the pressure to remove the gauge I noticed it kept pressure for a LOT longer than normal. I mentioned it being odd and the guy asked me what would cause it. I said it sounded like air in the fuel lines because air is compressible and explained how the air bladder in the tank in a home water system worked. Then I let a little fuel out of the rail and then out came a ton of air and the car started fine after that. He asked what would cause that and I suggested he start saving for a pump (friends daughters boyfriend). I also suggested when the car would stall out like it did to open the hood and let that air out because engines can't run on air alone. A week later the pump died completely. So yeah, pay attention to how long the fuel rail holds pressure while bleeding it off too.

[Rootie524]

i smelt fuel and now found out its giving spark and on attempts to start it you could hear it kinda chugging. like it was almost ready to start.

i sprayed some starter fluid in and then tried to start it and it actually then fired up. and then shut off after alittle. did it again and then it stayed running on its own. so its like it needed it to initially start it and it then got everything in working order again.

now that its running somewhat stably i dont have RPMs showing up on my tach. now i need to know details about interchangeability.

as you all know its a 3400 engine in a car that was a 3100. i have a 3100 crank position sensor (brand new) behind the harmonic balancer right now and my 3100 PCM. and no RPMs are showing but other than that it seems fine. do i need a 3400 computer? or would a 3400 crank position sensor work with a 3100 computer?

basically the question is can i get away with just the sensor being 3400 or does it all need to be 3400 or is there another reason why im not getting a signal?

[pocket-rocket]

The sensor is the same. The PCM won't care if it's a 3100 or 3400 either, as long as it knows things like injector size, ect. You could have a bad instrument panel. Do you get RPMs with a computer hooked to the diagnostic port? If you get RPMs on the computer through the port but not on the dash, I would be looking into getting a new cluster. At this point, even a cheap ELM interface would work just fine for getting a datalog to see if the PCM is displaying RPMs. I would think it would now that the engine is running.

[Rootie524]

yeah im using the same fuel rail that was on my 3100 so im good in that sense. RPMs started working. they showed up on my computer program before the cluster like you said and this may sound weird but i dont think they were working because my battery was really low or there was a temp. electrical issue. because they didnt work. then my battery got too low to start it so i charged it up good, then the tach worked. so idk. at any rate..it works now!

idled at around 1500 for some time then finally went down to around 900..so i assume some fine tuning will be in order lately.

now..from one problem to the next. i dont really know if this is much of a problem. there is a bit of white smoke coming out of the tailpipe and there are plumes of white smoke coming out of the oil fill in the valve cover. im talking like nuclear power stack smoke. first possibility is too much oil. when the dipstick tube was removed it broke off in the block and i have yet to get the piece of it out. so i can't put a dipstick tube in there to check oil. when it gushed oil out i questimated it to be about 4qts..so i put 4 qts in on top of what i expected to be left. im now thinking what i thought was 4qts might have only been 2...so i could have a tad too much oil in there. would that cause the smoke out the oil..

my guess for some out the tail pipe is bad gas. the cars been down since November. it's had the same gas in since. i would assume that is also whats causing some start up and stability issues. correct me if im wrong. thanks! we are getting there

[pocket-rocket]

I would think the smoke out of the tailpipe would really be steam from condensation in the exhaust. I wouldn't worry about it until you get it down the road a bit (after fixing the dip stick), unless it feels overly moist when you put your hand in front of it. As for the dip stick, if it's below the outside of the block, you could do it 1 of 2 ways. Either drop the pan and pound it out towards the pan, or pound it into the pan and hope it falls by the drain plug and fish it out with a magnet. Or better yet, stick a magnet on a stick in the drain plug hole and pound it it hoping it hits the magnet when it falls. I would try the magnet on a stick idea first, personally. Then if you can't fish it out, then move on to dropping the pan. If the gasket is fairly new, I wouldn't bother changing it since it's the molded rubber type that do a good job of resealing. Just be sure to sillycone the corners where the rear main cap and timing cover hit.

[Rootie524]

yeah ill end up having to do that. its kind of imperative to know oil level. but would oil being over filled cause my smoke stack out the valve cover?