L98 Engine Won't Start
Thread Starter
Instructor
Joined: May 2011
Posts: 213
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From: Miramar Florida
L98 Engine Won't Start
I've got a 87 L98 engine that won't start. Engine will turn over & plugs are firing but will not start & run. Last thing I did before the problem was adjust the timing on the distributor about 2 degrees but it ran fine after the adjustment. The next day it would not start & run. It's getting fuel to the rails, I measured 40 psi. What could be the issue? Any ideas?
Burning Brakes
Joined: Sep 2008
Posts: 810
Likes: 58
From: Alva Florida
Timing Chain (not likely). Run a compression test on a cylinder or 2. Air + fuel + spark (at the right time)+ compression should run.
Also (of course) the ECM needs to control ignition timing correctly also. It also controls the Injector Firing. You have batch fire injection so all the injectors should pulse at the same time. I have heard about a "noid" light to help diagnose that, but have never used one myself.
Of course the Factory Service Manual will help you troubleshoot it correctly.
There is lots of help to be had from experts on this forum, also.
Good Luck.
Also (of course) the ECM needs to control ignition timing correctly also. It also controls the Injector Firing. You have batch fire injection so all the injectors should pulse at the same time. I have heard about a "noid" light to help diagnose that, but have never used one myself.
Of course the Factory Service Manual will help you troubleshoot it correctly.
There is lots of help to be had from experts on this forum, also.
Good Luck.
Last edited by cadmaniac; Jul 24, 2013 at 02:48 PM.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
Get a noid light and see if the injectors are firing first.
You can also follow this flowchart:
http://www.chevythunder.com/ses_chart_a3a.htm
You can also follow this flowchart:
http://www.chevythunder.com/ses_chart_a3a.htm
Burning Brakes
Joined: Jun 2003
Posts: 849
Likes: 1
From: dubuque iowa
I've got a 87 L98 engine that won't start. Engine will turn over & plugs are firing but will not start & run. Last thing I did before the problem was adjust the timing on the distributor about 2 degrees but it ran fine after the adjustment. The next day it would not start & run. It's getting fuel to the rails, I measured 40 psi. What could be the issue? Any ideas?
you state turns over and plugs fire...how is this being verified that the plugs are firing? are you physically removing them and cranking engine while plug body is grounded? checking spark on plug wire itself with timing light or other spark testing equipment? or is the engine trying to start(like sputtering, speeding up but just not quite starting?
if spark is truely there and i mean truely firing plugs not just the wires then i would recoment the quickest easiest way to determin if its a fuel problem by getting it to fire by spraying a little start fluid into the plenum area and see if it fires, tries to start or actually start.
also does it smell heavy of fuel when cranking? if so try holding accelerator pedel to floor while cranking to make sure its not flooding itself on trying to start.
basically like i said the description of what its doing and how its acting is just too vague to tell you how to continue to diognose without just telling you to test everything step by step from a flow chart .
Last edited by ladystoy69; Jul 24, 2013 at 04:16 PM.
Thread Starter
Instructor
Joined: May 2011
Posts: 213
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From: Miramar Florida
you state turns over and plugs fire...how is this being verified that the plugs are firing? are you physically removing them and cranking engine while plug body is grounded? checking spark on plug wire itself with timing light or other spark testing equipment? or is the engine trying to start(like sputtering, speeding up but just not quite starting?
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Burning Brakes
Joined: Jun 2003
Posts: 849
Likes: 1
From: dubuque iowa
pull out a plug or 2 and look at them, what do they look like? black? clean white, wet, dry? what do they smell like? fuel or not really anything?
Thread Starter
Instructor
Joined: May 2011
Posts: 213
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From: Miramar Florida
Ok, I just went through & pulled all the plugs. They were a little foul with soot but not terribly bad, but I went ahead & cleaned them but basically had the same result when I started the engine. I was able to get the engine started & maintain it for a moment by patting the gas pedal but it would immediately die when I stopped patting. Any ideas?
Thread Starter
Instructor
Joined: May 2011
Posts: 213
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From: Miramar Florida
I only have a code reader but I'm not getting any codes. I would think that if it was the IAC, that I could maintain the engine by holding the throttle. When I hold the throttle, the engine dies. It only try's to keep running when I pat the throttle.
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
Your theory would work with the CTS though? Personally, I'd start looking at fuel pressure leak down, and fully functioning TPS
Team Owner
Joined: Jul 2004
Posts: 28,519
Likes: 3,310
From: Hartford WI
FYI, Cliff made a comment the other day that kind of surprised me. The only thing in the programming shown as using the IAT is the EGR caveat. If you know of another please point it out.
Your theory would work with the CTS though? Personally, I'd start looking at fuel pressure leak down, and fully functioning TPS
Your theory would work with the CTS though? Personally, I'd start looking at fuel pressure leak down, and fully functioning TPS
That too could be an issue. He'd have to get a scanner to be reading the values.
Instructor
Joined: Jul 2013
Posts: 164
Likes: 0
From: Palm Harbor FL
Ok, I just went through & pulled all the plugs. They were a little foul with soot but not terribly bad, but I went ahead & cleaned them but basically had the same result when I started the engine. I was able to get the engine started & maintain it for a moment by patting the gas pedal but it would immediately die when I stopped patting. Any ideas?