I'm new to the forum, I'm not a mechanic and I'm over my head. Just bought my first Vette, 86 vert. I've replaced the engine with a new short block, new valves, new high torque starter, new a/c compressor & dryer, etc. I've put about 200 miles on the new engine and it runs perfectly. That is after you get it started. First start of the day is almost impossible. It seems as if it doesn't want to fire. When you finally get it started, it runs for a few seconds, even at about 22 - 2300 RPM, then just dies. There's nothing you can do to stop it. If I keep trying to re-start, I can pretty much run down the battery (which is also new). It just doesn't want to fire up. Sometimes it will try to start only if you put the gas pedal all the way to the to the floor. You can really smell the gas after awhile, too. I tried for several hours to get the car started today. When I finally did, it ran perfectly, idled perfectly. It seems like as the engine warms up (h20 temp around 180 or above), it becomes a little easier to fire. I have no clue as to how to try to begin to troubleshoot this. It's like either too much fuel is being injected initally or suddenly, not enough gas is being pumped to the engine and I have no idea why it suddenly dies. Usually on the first crank, the car will fire but after it dies (in about 30 seconds or less) that's when it has problems igniting. The fuel injectors are only a few months old and are very clean. I do have alot of repair paperwork on this car and found that the previous owner had the car in for the same thing to which they replaced the "electrical module". Obviously that didn't do it (or maybe it did do it and it's time to replace it again). I don't think this is a major problem. I'm thinking some sort of module or "choke" problem. I'd really appreciate any assistance as to where to start. I know there's alot of "vette tech pros" here and I could really use the help. Thanks in advance.

 

Is the ECT sensor plugged in and working properly. The ECM enriches the mixture, like a choke, when it thinks the engine is cold. If the ECM thinks it is -40° F (like it would with the ECT sensor dead or disconnected), it will send a really rich mixture. Also, when you floor the pedal while cranking, the ECM goes onto "clear flood" mode and shuts off the fuel to the engine. That is probably why it starts with the throttle open all the way. Do you have any trouble codes set? You really need a FSM and a DVOM, and get to trouble shooting.

RACE ON!!!

 

You don't need to be a great mechanic,but you do need a service manual,perferably a factory one.Could also be the cold start switch.It's located on the front of the engine,by the ECT.It controls the 9th injector,which is for fuel enrichment on a cold engine,basicly a choke,but technicly not.Good luck.

 

Is the "service engine soon" stuck on ?? Have you tried to see if there any stored codes ??

 

No. Service Engine Soon light is not on although it does come on sometimes while driving. So does the Low Coolant light but the coolant is new and not low. Something is dumping fuel and I can hear a "click" just before it shuts down although I'm not sure where it is coming from. We bypassed the #9 injector and it didn't do a thing. Also replaced the coolant temp sensor because the old one had a crack in it. I'm thinking that maybe it is not the right one? ... although it has been working. Once the engine heats up to about 200 or so it becomes easier to start. It also runs perfectly once I get it running. I just can't rely on it to start again once I turn it off. I may be way off base but could part of the "security system" be a "fuel-shut-off-valve"? Or is the original security system just tied to the horns?

 

You are going to be fumbling around in the dark without a FSM. And a scan tool - to see what the ECM sees for all of the sensor inputs.

"Heard a click". Fuel pressure - is the relay staying pulled in? Have you checked the fuel pressure while all this is going on?

Have you checked to be sure that you have Spark when it won't start? Pulse at the injectors?

Is the ignition timing set right - which may not be the same number as the "factory" setting with a different cam. Try advancing the timing to see if it'll fire up any better/sooner. Or not.

The engine Fires up using the baseline timing set at the distributor. At about 400 rpm (as it lites off) the ECM takes over timing control (from the module in the distributor - which Does have a small timing advance step built into it) and advances to whatever the PROM program is supposed to be doing. It's that below 400 rpm timing that is important to how easily/quickly the motor fires up.

Actually - since you have had the Whole motor apart - is the Camshaft in there right - is the cam centerline timing in the right place? A quick check of cranking compression might be interesting.

Security system - No, has nothing to do with starting or running, other to disable the actual Starter solenoid. If it cranks the security system is happy.

 

Welcome to the forum and congrats on your new ride

It does sound like the ECT sensor...but that's just a guess.

Three things you need; A fuel pressure guage, a digital voltage ohm meter and a year specific factory service manual. For the FSM, check on ebay.

It also sounds like your throwing a code with your light coming on, do you know how to pull the codes?

 

The "Check Engine" light coming on at any time proves there are unresolved problems. They may or may not be involved with all your troubles, but first things first. Cure known problems before you start chasing shadows. Pull the code(s) and use the trouble shooting charts in your FSM to cure them without throwing money at the problem(s). The "Low Coolant" light may indicate your cooling system needs to be burped, IE: not full, air in the system.



What was the location of the sensor you replaced? If your '86 has an aux fan there are three coolant temp devices, not to mention other temp sensors on your engine.



If the fuel pressure relay isn't "staying pulled in" (never heard if it ever dropping out) the oil pressure switch will continue to send power and keep the fuel pump running.

RACE ON!!!

 

UPDATE: Wow. I also have a '74 VW Karmann Ghia. Looks like that's more my speed. No high tech modules or sensors ... just 4 cylinders and 40 hp! Anyway, here's an update on what we've done. I have a very good friend and mechanic by trade working on the car with me. We have totally bypassed the #9 injector. This only happens now when the car is cold. The car starts, runs for a minute or two, then shuts off like you just turned the key off. It's an abrupt shut down. The Computer is reporting no errors. We've done over 50 tests. We've eliminated fuel pump issues, and temp sensors. We've put a pressure gauge on the engine. Everything is fine. What has us puzzled is after the car shuts off, you have to floor it to get it started again. But when the car shuts down, it's not flooding out. The engine runs very well after it heats up (about 200 or so). Just thought I'd pass the info on. It's like there's a "kill switch" in the engine that abruptly shuts things down after a minute or so but the car is all stock, even the security system. It's like you just turned off the key.

 

The "Check Engine" light is evidence the ECM has seen problems. Maybe you erased the codes before you got around to checking them.

In any case, with your "good friend and mechanic by trade" helping, you don't seem inclined to accept the free, experienced, advice offered in response to your plea. Good luck, and...

RACE ON!!!

 

On the contrary and with all due respect CFI-EFI, I'm printing out every response and referring it to my "good friend and mechanic by trade" hoping something will work. When I bought the car, the #6 rod bearing was shot. The mechanic put in a short block and from there literally built a new engine, all in a week. The engine, I assure you runs unbelievable when it has heated up and most everything is new. You've got to understand I'm not a mechanic so alot of this is "greek" to me and I want to make sure I get it right. Rons85's response made alot of sense, especially about the below 400 rpm timing and I sincerely thank everyone for their time and input. Please have a little mercy. This is all new to me. Sorry if anyone got offended.

 

You didn't offend me by any means.I'm not too sure if anyone could.But if your mechanic,and I'm not saying that he's not good, if he didn't know about setting the base timing properly,you guys need a FSM,and that's all there is to it.You can keep throwing parts at this,and I'm sure you will eventualy get it.But you shouldn't have to.

 

If by FSM you mean the hand held computer that connects under the dash and spits out all the codes, what I'm saying is we have one and it is showing that everything is functioning properly and "the mechanic" knows how to use and read it. And the "scan tool" is different from the FSM, correct? I was just simply hoping that a previous Corvette owner had maybe experienced the same problem. I'm not trying to get free advice. Was just hoping for a clue or two. And as far as eventually "getting it", we will. It's just a matter of time and elimination but you are so right, it shouldn't have to be that way.

 

No! and Yes! See post #8 where you previously ignored the link to the FSM.

RACE ON!!!

 

CFI-EFI: Ouch! You're tough! Your "link" that was NOT previously ingnored took me to Helm, Inc. where you buy Service Manuals, etc. (here's the url to your link) ... http://www.helminc.com/helm/homepage...ighlight=adfac
I saw nothing about an FSM so I moved on. Sorry. Didn't mean to be that stupid. Will educate myself as to exactly what an FSM is before I make any other posts.

 

Factory service manual ,FSM.

 

Boy do I feel dumb. Thanks!

 

The Factory Service Manual is produced for Chevrolet (and some others) by Helm Inc, hence, the link. Buy one!

RACE ON!!!

 

<<The Factory Service Manual is produced for Chevrolet (and some others) by Helm Inc, hence, the link. Buy one!>>

I just did. Thank you. Told you I was a "newbie".

 

Just wanted everyone to know we replaced the EST module and the ignition module and the problem has been solved. Thanks for everyone's time and assistance. At worst, I now know what an FSM is! <vbg> Thanks again.