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No start issue

dellstopjeep

dellstopjeep

NAXJA Forum User
Location
KUNA, ID
91 Comanche auto, came down off a rock Sunday and vehicle just died. Now it will only crank but will not fire. Good fuel pressure good spark so its not a cps. Map sensors fine everything appears plugged in still, any ideas I'm missing before I really see if its a timing chain issue? Just not convinced this is really my issue yet.
 
check O2 sensor, CTS, IAT? Check if you have sensor bus power (7 volts or so) and power at the ASD relay signal to the engine electronics (green/orange wire, 12 volts)?

Check grounds? Some like to come loose.

Check compression to rule out timing chain issues? Should only need to check one cylinder.
 
I'm not sure that it can be, but it can't hurt to check. Pretty sure the signal isn't used till closed loop is entered but IIRC the signal is referenced off the same reference voltage line as a few others...

CTS = coolant temp sensor. I am reasonably certain that the CTS, IAT (intake air temp sensor), MAP, and TPS are the most important sensors used during cold/open-loop startup.
 
most important sensor is the CPS---crank position sensor..... will not run without one...
 
AFAIK he already checked that... and has been told to check it probably 5 times already. And he already said it's not the CPS, since he's got spark.
 
Check the fuel pressure AND volume.

You may have crushed a fuel line dropping off the rock.
 
joe_peters said:
Check the fuel pressure AND volume.

You may have crushed a fuel line dropping off the rock.
Click to expand...


that's what I was thinking.

Even so, as I mulled it over, it would probably still run albeit poorly, even if his fuel lines were taco'd/crimped/etc...

OP are you checking spark at the plug? Check all 6?

Just trying to think of the possibilities.
 
also, what about your exhaust being sealed/crimped shut at any given point?

Would enough backpressure cause a no start?

I would be looking for any obvious scrapes/scratches, etc. (you probably already did that...)
 
I doubt that, if after multiple attempts at debugging it and starting it it still has fuel pressure to spray him in the face, the pump's running fine and fuel is at least getting to the rail, so it should at least try and run even with a restricted line. Worth looking at though, since it takes 5 minutes.
 
kastein said:
I doubt that, if after multiple attempts at debugging it and starting it it still has fuel pressure to spray him in the face, the pump's running fine and fuel is at least getting to the rail, so it should at least try and run even with a restricted line. Worth looking at though, since it takes 5 minutes.
Click to expand...

Yup, agreed. Stranger things have happened to me, though. :D :D
 
To follow up I must have not relieved fuel pressure fully on trail. I checked again and had no pressure after cranking. Pulled fuel lines off nothing came out cranking. Fuel pump not kickin on. I checked voltage at plus. 6 volts...seem right? I jumped pump and it kicked on and sounded fairly healthy.
 
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