96 Mark VIII Cranks but no start when engine warm?

Chuckthetom

New LVC Member
Joined
Dec 19, 2021
Messages
7
Reaction score
1
Location
Sacramento, CA
Hello all,

I’ve been stumped on my 96 Mark VIII randomly not starting when the engine
Is warm. It drives great, but when I turn it off it and it sits for 10 minutes it won’t start again. Cranks great, but does not try to start. After an hour or so it’ll start right up and run great again. I have a p1537 code that I’ve been trying to resolve also but I think it’s a separate issue.
It Had a major oil leak recently so I changed the oil filter adapter gasket, did an oil change, and changed the coolant. Leak fixed. It never did this until after the oil filter adapter gasket repair. Not sure if it’s related either. I’ve been reading 100s of forum discussions and its so many possibilities. Anyone have this issue with their Mark VIII?
Thanks for any info.

Tom
 

driller

Dedicated LVC Member
Joined
Mar 21, 2004
Messages
3,795
Reaction score
77
Location
West Virginia
Have you tried to depress the accelerator to the floor when cranking?

From your description, it sounds like it is flooding during the warm restart. If that is the case, when the accelerator is held to the floor for wide open throttle, the fuel injectors are shut off which helps clear the flooded condition.
 

Chuckthetom

New LVC Member
Joined
Dec 19, 2021
Messages
7
Reaction score
1
Location
Sacramento, CA
Have you tried to depress the accelerator to the floor when cranking?

From your description, it sounds like it is flooding during the warm restart. If that is the case, when the accelerator is held to the floor for wide open throttle, the fuel injectors are shut off which helps clear the flooded condition.
Hi Driller,

I believe I have tried it a few times. I've tried many combinations of pressing the gas pedal all the way down or pumping it. I can hear the fuel pump engage when I turn the key on. It doesn't seem to even try starting when the engine is warm (it cranks great though). I do have the p1537 IMRC (bank 1 stuck open) actuator code, which adjusts the air to the intake above or below 3000 RPMs via the actuator and a butterfly valve inside the intake. From what I have read about it I don't believe this would cause the engine not to start when it is warm. Would it? I've checked the vacuum hoses and the IMRC actuator does hold suction. Does it sound like a fuel issue, maybe a fuel filter? It is puzzling that it runs great for as long as I drive it on a cold start. It will also start right up again without any problem, only after 10 minutes of sitting cold will it cause the crank and no start issue. I switched relays around under the hood to see if made a difference. They seem fine. No blown fuses. I don't want to start replacing random parts hoping to get lucky. I wish I could narrow it down. I've seen similar issues on different types of cars on forums, no no clear answers to the cause.
Thank you for any insight.
 

joegr

Dedicated LVC Member
Joined
Dec 10, 2005
Messages
21,111
Reaction score
2,075
Location
Gulfport
You might try spraying some starting fluid in the intake to see if it tries to catch. If it does, then it likely is a no fuel problem instead of a spark or flood problem.
 

Chuckthetom

New LVC Member
Joined
Dec 19, 2021
Messages
7
Reaction score
1
Location
Sacramento, CA
I will try spraying the starter fluid into the intake. Is this a two person job? One needs to be cranking it while one sprays the starter fluid I imagine. Thank you.
 

driller

Dedicated LVC Member
Joined
Mar 21, 2004
Messages
3,795
Reaction score
77
Location
West Virginia
Test for fuel pressure first. You can rent or buy a gauge to attach to the fuel rail schrader valve. Attach the gauge, turn the key on and see if you get pressure. The fuel pump runs a couple seconds when you key the ignition without turning it all the way to the start position. You may need to cycle the key on/off a few times to get a pressure reading.

If you have fuel pressure, your next move would be to check for spark.
 

xtriggerman

Well-Known LVC Member
Joined
Jan 7, 2019
Messages
243
Reaction score
79
Location
TN
I will try spraying the starter fluid into the intake. Is this a two person job? One needs to be cranking it while one sprays the starter fluid I imagine. Thank you.
You don't want any one spraying the intake manifold mouth while you turn the engine over. If the engine backfires it could cause a dangerous explosion in the hands of the sprayer. Just spray the inside of the mouth until slightly wet, then quickly get to the key and turn it over. If there is spark, it should fire up for a few seconds at least.
 

Chuckthetom

New LVC Member
Joined
Dec 19, 2021
Messages
7
Reaction score
1
Location
Sacramento, CA
Thank you guys. I really appreciate it. Probably won’t mess with it again for a couple days. I’ll try these things and let you know what happens. It’s my secondary car so I’m not without a vehicle right now thankfully.
 

Chuckthetom

New LVC Member
Joined
Dec 19, 2021
Messages
7
Reaction score
1
Location
Sacramento, CA
Update and not solved.

Problem continues. Update. When it won’t start, I spray a little starter fluid into the intake and it’ll start up with a little hesitation but then runs great. Per your guys’ recommendation, thank you. I hooked up a rubber tube to the top of the intake through the vacuum port on top dead center of the intake manifold (the one with a rubber cap on it) so it’s easy to spray starter fluid into if it won’t start. It’s still kind of randomly happening. Yesterday went into store for 30 minutes and wouldn’t start again. Sprayed one squirt of starter fluid and started right up and ran great. This is not ideal and only a temporary solution. Back to driving this car regularly. So I gotta fix it.

Checked fuel pressure and it’s good. I don’t recall the pressure off hand but it’s got plenty.

Tried pressing gas pedal to floor and made no difference. When using the starter fluid I do need to push gas pedal to floor.
Had my dad here trying to help me also and couldn’t figure it out.

Any ideas what to check next? Getting spark or it wouldn’t start at all.
Thank you.
 

driller

Dedicated LVC Member
Joined
Mar 21, 2004
Messages
3,795
Reaction score
77
Location
West Virginia
Need more info... short of that we're spitballing. Maybe check for codes again?

If it were mine, I'd be curious what the plugs looked like. That would require pulling the plugs when the 'no-start' happens. Obviously you would need to pre-plan.

Next random thought would be the IACV. I believe the idle air circuit is different between cold starts and warm starts. But again, just a guess at this point.

Another check would be the engine temp sensor. Thinking it may be giving false information to the PCM. Again, just a guess.
 

Chuckthetom

New LVC Member
Joined
Dec 19, 2021
Messages
7
Reaction score
1
Location
Sacramento, CA
Problem solved! Crankshaft position sensor. It would usually start with starter fluid so I ruled out it being a spark issue. Finally hooked up a spark plug tester on it when it was acting up to find that when it wasn’t starting I was also not getting spark. That lead me to a post about how crankshaft position sensors start to act when they are going out and everything lined up perfectly. Changed it out, bottom front of engine, next to the AC compressor, and no more issues. It was about $30 I think. You have to loosen the 3 bolts on the AC compressor to get it out which was a pain but definitely doable. Getting it to mimic the problem was difficult because it was intermittent, so the best way to make it happen was to start the car, leave it running at idle for 10 minutes or more and it eventually stalled out. When it stalled it also wouldn’t start up again. That’s when we (my dad and I) found the no spark issue. Thank god for pops helping me sort it out. Problem solved.
 

BILLBOATS

Dedicated LVC Member
Joined
Sep 29, 2014
Messages
590
Reaction score
23
Location
Akron
I will try spraying the starter fluid into the intake. Is this a two person job? One needs to be cranking it while one sprays the starter fluid I imagine. Thank you.
no it works with you spraying, it lasts over a minute, then jump in car to start. be quick
 

Chuckthetom

New LVC Member
Joined
Dec 19, 2021
Messages
7
Reaction score
1
Location
Sacramento, CA
Hello all,

I’ve been stumped on my 96 Mark VIII randomly not starting when the engine
Is warm. It drives great, but when I turn it off it and it sits for 10 minutes it won’t start again. Cranks great, but does not try to start. After an hour or so it’ll start right up and run great again. I have a p1537 code that I’ve been trying to resolve also but I think it’s a separate issue.
It Had a major oil leak recently so I changed the oil filter adapter gasket, did an oil change, and changed the coolant. Leak fixed. It never did this until after the oil filter adapter gasket repair. Not sure if it’s related either. I’ve been reading 100s of forum discussions and its so many possibilities. Anyone have this issue with their Mark VIII?
Thanks for any info.

Tom
Solved! It was the crankshaft position sensor. I wrote a longer post about it at the bottom of this thread. Thanks everyone for your input.
 

Members online

No members online now.
Top