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K5 won't start, getting gas, spark and air, please help!!!

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dawson444

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K5 won't start, getting gas, spark & air, please help **UPDATE, it runs but more ?s**

Well my truck ran about 2 months ago, I went out of town for 3 weeks, when I left I disconnected the batteries. I got back and started my truck up, I let it idle for a few mins, then I gave it a little gas. It started to act like it was going to stall so I let off the gas and was going to let the computer straighten the idle back out. Well it never did, and eventually stalled. Somewhere in there the check engine light came on. I tried to retsart it and it wouldn't. I pulled the code it was the MAP sensor, replaced the MAP sensor, but it still won't start. It kind of sputters now but won't just won't run. The injectors are firing and I can smell gas a little bit in the exhaust (it has always run rich) so I know it is getting gas. I pulled out a few of the plugs and they look good and are sparking, so what in the world do you guys thing is going on? Thanks!

Engine details:
88 K5 TBI
Chevy 355
Vortec Heads
Not many miles on rebuild
Holley 670 CFM TB
over sized injectors
custom computer chip burnt using a dyno
 
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What are all of the causes of a MAP sensor error? Particular error code might net you everything that can cause that code to be set.

Just as an example, a vacuum leak could probably set that code, doesn't mean the MAP sensor is bad, just that the MAP reading isn't what it should be given the engine conditions the ECM is seeing.
 
hmm ive got the same problem. just replaced all spark plugs, wires, distributor cap, rotor, and new injectors and cleaned up the TBI.
 
what does it do when you give it gas when its turning over?

Might want to check your fuses for a blown ecm fuse or a blown crnk fuse:confused: :confused:
 
when i gave it gas, it rev'd up like normal and held wherever i held the pedal at.

(sorry didnt mean to hi-jack thread)
 
I checked the crank and ECM fuses, they look fine. When I start it with no gas it just turns over, doesn't really sputter. When I give it WOT while starting it, that is when it sputters and tries to start, but won't. I have looked for vacuum leaks and can't find anything. I'm open to other suggestions!
 
got me..... could be a lot of things, vacuum leak, timing(don't know how it would be off), Bad gas or water in gas, etc. Does it all sound normal when you turn it over? No clanking or knocking?

Get a timing light on it just to be sure.

My truck was doing this same thing when the timing was off.

Try spraying wd 40 or carb cleaner on and around the manifold, tbi gasket, and vacuum lines while its turnin over. If it starts up and dies you have a vaccuum leak.


someone on an earlier post said something about the ecm being reset everytime the battery is takin off. Try taking the battery cables off again then hook them up, turn the ignition on and give it full throttle a few times before you start it. This should reset the tps. Also If the coolant sensor hasn't gotten up to temp since the battery was takin off it won't run right until it registers on your temp gauge. It will run way too rich until it gets up to temp.

Just as an example, a vacuum leak could probably set that code, doesn't mean the MAP sensor is bad, just that the MAP reading isn't what it should be given the engine conditions the ECM is seeing.
Click to expand...

If none of this works im stumped.:confused: :confused: :confused:
 
dirtwarrior17 said:
someone on an earlier post said something about the ecm being reset everytime the battery is takin off. Try taking the battery cables off again then hook them up, turn the ignition on and give it full throttle a few times before you start it. This should reset the tps. Also If the coolant sensor hasn't gotten up to temp since the battery was takin off it won't run right until it registers on your temp gauge. It will run way too rich until it gets up to temp.
Click to expand...

that isn't how the EFI ECM works.


do you have a functioning EGR?
remove the oil cap, and see if your rockers are moving and check to see if they seem close to the sequence of the positions of the pistons
Check to see if your purge solenoid is working correctly

I can make a huge list of all the things to check thou.
 
If you really want to reset the ECM (which will clear any codes) all you have to do is pull the fuse for it. No reason to pull the battery cables.
 
Well I turned the distributor some today and it finally started, it didn't run that great, but it ran. Now the question is what in the world is going on???? I pulled out the distributor to look at the gear and it looks good. What happened? It is seeming like the timing chain might have jumped, but why now? The motor doesn't have more than 2k miles on it and it has run fine during that time. I did replace the timing chain when I rebuilt the motor. Also if the chain did jump, why didn't the truck die right after it started to not sound right? I asked my mechanic and he seems stumped, as well as myself, anyone have any ideas? I really don't want to start tearing into it and find out that the chain looks fine. Thanks!
 
its the timing................................

I spent days trying to figure out what was wrong with my truck until i realized that i didn't take the brown wire off for the advance when i timed it.
 
dirtwarrior17 said:
its the timing................................

I spent days trying to figure out what was wrong with my truck until i realized that i didn't take the brown wire off for the advance when i timed it.
Click to expand...

i just saw this, but that what I was going to say too.
 
But if it is the timing, how did it get off? The dist was down tight. I am also not sure if it will run that great if I was to time it right now, I didn't mess with it that much after i got it to run.
 
couldn't tell you.... but if you move the dist and it runs better than you have found part of the problem. I would time it again and then go from there. It doesn't take much to throw your motor off when it comes to timing. Also the timing chain could be a part of it. What do you mean you didn't mess with it that much? did you move the dist before?
 
I know it doesn't take much to throw the timing off, but for it to be off enough for it to not run period, thats what gets me. When I say I didn't mess with it much, I didn't let it run that long because it didn't seem to want to idle that great. I didn't put a light on it, I just twisted it and got it to run.
 
with a small vacuum leak and timing that is a little off it will not want to start up or idle. It's hard to pinpoint it until you start trying things and checking them off the list.

try some of the stuff that was metioned in earlier posts like the vacuum leak check and reseting the ecm.

I'm almost out of ideas.:confused: :dunno: :deal: :1zhelp:
 
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