Please help, engine wont start
Thread Starter
Drifting
Joined: Dec 2007
Posts: 1,672
Likes: 8
From: Sumter South Carolina
Please help, engine wont start
I just finished putting the engine back together save a few vacume lines and air pump. I get spark, engine turns but no gas. If I turn on the accesory from the key shouldnt I get fuel preassure. The line is bone dry.
How can I test to make sure my fuel pump is working. I hate just turning the engine w/ out it running. any other things to check for? please help.
Thanks, any suggestions will help. Ive been working really hard on this thing and still no luck.
Mike
How can I test to make sure my fuel pump is working. I hate just turning the engine w/ out it running. any other things to check for? please help.
Thanks, any suggestions will help. Ive been working really hard on this thing and still no luck.
Mike
Thread Starter
Drifting
Joined: Dec 2007
Posts: 1,672
Likes: 8
From: Sumter South Carolina
gas is all new gas in tank and line, the timing I have no idea because never have started the car since I bought it disasembled. I cant put a timing light on it util I have it running. I tried just putting the distributer centered as best I can. I will try the spark plug thing really quick.
Race Director
Joined: Dec 2006
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It should have a noticable amount of gas on it if you've been turning her over with no start.
You've got fuel pressure to the injectors, right? But do you know if they are firing?
Your car is an 87 right? I don't know them. But you should be able to hear the injector fire with a mechanic's stethescope, long screw driver, or see that it is getting pulse with a noid light.
You could try about a three second squirt of starter spray into the TB also.
You've got fuel pressure to the injectors, right? But do you know if they are firing?
Your car is an 87 right? I don't know them. But you should be able to hear the injector fire with a mechanic's stethescope, long screw driver, or see that it is getting pulse with a noid light.
You could try about a three second squirt of starter spray into the TB also.
Last edited by 94z07fx3; Jan 16, 2008 at 04:06 PM.
Thread Starter
Drifting
Joined: Dec 2007
Posts: 1,672
Likes: 8
From: Sumter South Carolina
hooked up a noid light to injector wire and when key is in accesory position it says it has constant charge. this seems odd to me. There is definatly fuel preassure becaus when undo the fuel line it squirts everywhere. but no fuel in cylenders.
I think we could try going to get carb cleaner and spraying down TB. will that run off that (granted will be a rough run)?
I think we could try going to get carb cleaner and spraying down TB. will that run off that (granted will be a rough run)?
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Race Director
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The injector's pulse is a ground provided by the comp. There should be a constant 12V there and when it pulses it will have a ground.
Maybe an L98 guy will chime in and tell us what event triggers injector pulse on your motor. There has to be some way the comp knows the engine is spinning and where it is. If you have a cam or crank position sensor double check that it is connected properly and you can even back probe those with an analogue volt meter and should see it go from 5 to 0 volts and back once or twice for every revolution. Again this is just general knowledge I'm sadly out of my depth when discussing L98s.
Maybe an L98 guy will chime in and tell us what event triggers injector pulse on your motor. There has to be some way the comp knows the engine is spinning and where it is. If you have a cam or crank position sensor double check that it is connected properly and you can even back probe those with an analogue volt meter and should see it go from 5 to 0 volts and back once or twice for every revolution. Again this is just general knowledge I'm sadly out of my depth when discussing L98s.
Last edited by 94z07fx3; Jan 16, 2008 at 04:17 PM.
Race Director
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Ok I found an article (clicky) that says the comp knows the engine is spinning and where it is from a reference pulse from the distributor. Make sure there isn't a little pigtail off on the distributor. I've never seen one or a picture but I suspect it would be a three wire connector. You can try all the various combinations of back probing it with a volt meter to see if it's working IE A+ B-, B- A+, A+ C-, A- C+, B+ C-, B- C+ while someone else cranks. The sensor will need power so you'll have to back probe it while it's connected. Without this signal, the comp won't know when or if to fire the injectors and won't send a pulse(ground).
Thread Starter
Drifting
Joined: Dec 2007
Posts: 1,672
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From: Sumter South Carolina
ok, i cant try that today but I will tomorrow. I just got some carb cleaner and the engine shot and fired but couldnt keep it up. but that means injectors are not firing. I guess the first step is to try to find a loose connection. but what after that? is there away for the car to run w/ out comp telling it when to inject? just follow what the distributer is doing?
Intermediate
Joined: Jan 2008
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I had the same problem when I put my 91 L98 back together. I had 4 injectors bad and the distributor was off one tooth. When I had the intake manifold off I ran it through a cleaning vat with a PD680 type product. I think that is what caused them to go bad. I was getting some chugging though when I attempted to start it but it just wouldn't turn over.
Last edited by Radco10; Jan 16, 2008 at 09:15 PM. Reason: more info
Team Owner
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From: Summerland B.C. Canada
5th Gear
Joined: May 2002
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From: Goddard KS
I assume that you've found your problem by now, but when I bought my 90 with the dash disassembled, I found out the hard way that the SIR (airbag system) fuse has to be installed before the fuel and ignition systems will work. I plugged the fuse in and it started right up.
Safety Car
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From: :45 minutes from everywhere / E-I-E-I-O
I assume that you've found your problem by now, but when I bought my 90 with the dash disassembled, I found out the hard way that the SIR (airbag system) fuse has to be installed before the fuel and ignition systems will work. I plugged the fuse in and it started right up.
No oil pressure will stop the fuel pump, but it should still give up an initial fire... Sounds like he ain't even gettin' that.
Thread Starter
Drifting
Joined: Dec 2007
Posts: 1,672
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From: Sumter South Carolina
I havent had time to work on it yet, going to do that tomorrow and check at least the EGR valve, make sure it ain't sticking and I figure I can try taking the battery to autozone to get it fully charged or hook up a trickle charger. I dont think any of these will be the problem but hey, never know.
How would I go about testing all the sensors? like oxygen, throttle position, MAF, etc. Can I just hook up volt meter to where the wire enters the ECM w/ the key to the accesory/ run position? or does the car need to be running?
How would I go about testing all the sensors? like oxygen, throttle position, MAF, etc. Can I just hook up volt meter to where the wire enters the ECM w/ the key to the accesory/ run position? or does the car need to be running?
Melting Slicks
Joined: May 2007
Posts: 2,171
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From: Warwick RI
I havent had time to work on it yet, going to do that tomorrow and check at least the EGR valve, make sure it ain't sticking and I figure I can try taking the battery to autozone to get it fully charged or hook up a trickle charger. I dont think any of these will be the problem but hey, never know.
How would I go about testing all the sensors? like oxygen, throttle position, MAF, etc. Can I just hook up volt meter to where the wire enters the ECM w/ the key to the accesory/ run position? or does the car need to be running?
How would I go about testing all the sensors? like oxygen, throttle position, MAF, etc. Can I just hook up volt meter to where the wire enters the ECM w/ the key to the accesory/ run position? or does the car need to be running?
Try this first
You said your timing is close but I would bring it to TDC first and verify it.
Turn your key on(accessory won't do a thing) and listen for the fuel pump to cycle on so at least you know it is primed.
Crank it a couple of times and if nothing spray some starting fluid in the TB and try it. If it fires at least you know it is a fuel problem.
All the sensors will make it run like crap but it should run.
Drifting
Joined: Apr 2007
Posts: 1,339
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From: port charlotte fl
I just want to check with you as you say "I just put the engine back together "that you did spin up the oil pump and saw some oil pressure on the gauge before you dropped in the distributor and tried to start it.If you didn't go back and do that before any more attempts.
When you turn the key on the Vats system energises the fuel pump enable relay and the start enable relay.The fuel enable runs for two seconds(enough to supply the injectors)If the car starts the oil pressure closes the oil pressure switch which turns on the fuel pump.Simplest way to check the pump is to undo the schrader valve on the fuel rail and turn on the ignition and it should **** out everywhere.NO smoking please.As for timing it's so easy to put the thing at TDC on the compression stroke on No1(front cyl drivers side)line up the rotor with No 1 plug and bingo.Do the fine tuning afterwards.
When you turn the key on the Vats system energises the fuel pump enable relay and the start enable relay.The fuel enable runs for two seconds(enough to supply the injectors)If the car starts the oil pressure closes the oil pressure switch which turns on the fuel pump.Simplest way to check the pump is to undo the schrader valve on the fuel rail and turn on the ignition and it should **** out everywhere.NO smoking please.As for timing it's so easy to put the thing at TDC on the compression stroke on No1(front cyl drivers side)line up the rotor with No 1 plug and bingo.Do the fine tuning afterwards.
Thread Starter
Drifting
Joined: Dec 2007
Posts: 1,672
Likes: 8
From: Sumter South Carolina
I just realized this was an old post and I put up a new one w/ updated stuff on it. but I did track down fuel problem was a fuel pump relay, and a power wire was severed to the ECM and so now it cranks but wont Idle.
http://forums.corvetteforum.com/show....php?t=1928206
well I dont think that is the problem because after turning over and pumping gas It runs. I have to keep the gas pedal pressed to 30% to keep it going but it does stay on. For some reason my dash isnt working, just lights up but the oil preassure gauge does work on the dash and it reads like 1-3 when turning engine over then once it starts I get a reading of 80. I don't know if that is accurate or not.
I will reset distributer to TDC and then leave it alone and try a fully charge battery. Then, Like I said going for the stuck EGR valve.
http://forums.corvetteforum.com/show....php?t=1928206
well I dont think that is the problem because after turning over and pumping gas It runs. I have to keep the gas pedal pressed to 30% to keep it going but it does stay on. For some reason my dash isnt working, just lights up but the oil preassure gauge does work on the dash and it reads like 1-3 when turning engine over then once it starts I get a reading of 80. I don't know if that is accurate or not.
I will reset distributer to TDC and then leave it alone and try a fully charge battery. Then, Like I said going for the stuck EGR valve.
Last edited by rithsleeper; Feb 1, 2008 at 11:18 AM.