Bahhh !! Cranks but won't start.

[tonylong]

New problem, I hope is bad fuel.
Just filled with Hess Premium, running somewhat rough, "surges" after some worm up. Been happening for about a week of casual use, topped it up with Exxon permium (about 1/3 tank). Slight improvement.

Now - won't start while running errands. Tried several times, walked home, got Jeep, finished errands, stopped by where Vette parked, tried it again, no joy.

Had some beers, two hours later tried again, got her going, drove right home, walked back to get Jeep.

It cranks good but no start, don't think it's ignition because of the prior stumbling, and the fact that it did eventually start. Electricals usually don't give warning shots and when they fail - it's usually dead until something is actually fixed.

I still suspect bad fuel that may have clogged the filter, or jammed the fuel pump. She never liked Hess gas, I used it because Hess is all american, no arab. Jeep never had any oroblem with Hess, Vette always ran a little rough.

Not throwing any codes, or Engine Check lit.

How can I easily check if ignition is present, How can I check if fuel is present??

I need suggestions/opinions.
Thanks for any help.

 

[bill5674]

well a quick way to check spark is to just pull plug wire at the spark plug and hold about 1 inch from ground.should have a nice crisp spark when cranking. as far as fuel hook up a pressure gage to the fuel rack and note pressure .think its about 40 -50lbs.do a search for right numbers. but have to say it sounds like an ign. module had same systems with mine .... no start when hot ..or the right way is get the factory service book,it has a, no the best trouble shooting guide out there.

 

[gmjunkie]

well a quick way to check spark is to just pull plug wire at the spark plug and hold about 1 inch from ground.should have a nice crisp spark when cranking. as far as fuel hook up a pressure gage to the fuel rack and note pressure .think its about 40 -50lbs.do a search for right numbers. but have to say it sounds like an ign. module had same systems with mine .... no start when hot ..or the right way is get the factory service book,it has a, no the best trouble shooting guide out there.

L98 cars: 34-39
LT1/LT4 cars 41-47

 

[vetteoz]

Does it start OK cold? Can you smell fuel out exh pipe when it does not start? Leaking injectors fuel pump Fuel filter

 

[Hib Halverson]

(snip)

How can I easily check if ignition is present, How can I check if fuel is present??

I need suggestions/opinions.
Thanks for any help.

Check for spark as suggested earlier. You can check for fuel by getting a fuel pressure gauge for EFI and connect to the test fitting then turn on the key. The pump will run for two seconds with the engine off. The gauge should show the nominal pressure, fluctuate a little as the pump shuts off then should stablize at a slightly lower pressure and not drop off too fast.

Also, I strongly suggest the instructions in the Service Manual in the section on engine controls under "Cranks but Won't Run".

 

[tonylong]

Check for spark as suggested earlier. You can check for fuel by getting a fuel pressure gauge for EFI and connect to the test fitting then turn on the key. The pump will run for two seconds with the engine off. The gauge should show the nominal pressure, fluctuate a little as the pump shuts off then should stablize at a slightly lower pressure and not drop off too fast.

Also, I strongly suggest the instructions in the Service Manual in the section on engine controls under "Cranks but Won't Run".

Aha I do have the FSM, and that's gonna be my reading for today. The FSM has been engaged in supporting the end of a broken dresser, so now it's off to work for it.

 

[tonylong]

Check for spark as suggested earlier. You can check for fuel by getting a fuel pressure gauge for EFI and connect to the test fitting then turn on the key. The pump will run for two seconds with the engine off. The gauge should show the nominal pressure, fluctuate a little as the pump shuts off then should stablize at a slightly lower pressure and not drop off too fast.

Also, I strongly suggest the instructions in the Service Manual in the section on engine controls under "Cranks but Won't Run".

I'm not having any success in finding this in the FSM. There's plenty for "Does not crank". But nada on "Cranks but does not run". Nothing titled Engine Controls either. Can you point me to a section?
thanks

 

[John Robinson]

Since you have an FSM read the section on the Throttle Position Sensor (TPS)

You will note that it tells the ECM when and how much fuel to deliver to each injector. If the TPS goes bad it does not always send a code. Part of the function of the ECM TPS combination is if the engine becomes flooded the ECM will shut down the fuel to the injectors until a cylinder clears and fires while cranking. If this is what has happened to your car you can have someone crank the engine while spraying a small amount of choke cleaner or brake cleaner into the front of the throttle body. If the engine barks and runs try disconnecting the TPS and see if it will restart.

I learned this the hard way by replacing the ECM before I discovered the TPS was keeping my engine from running.

Good Luck

 

[bill5674]

okay ...under driveability and emissions,6e3-a-18-19 cranks but wont start.i would start with basics first.spark, fuel.if they check out then move on . bill

 

[tonylong]

okay ...under driveability and emissions,6e3-a-18-19 cranks but wont start.i would start with basics first.spark, fuel.if they check out then move on . bill

Found it, thanks. Now on to the analysis.

 

[LittleRedFlatBack]

Starting problems

I'm not sure if this will help, but I had a problem with my 90' (L-98) that drove me crazy for a while. The engine would turn over and start when cold, but after warming up, it wouldn't restart. I checked everything from fuel pressure to ignition and it all checked out fine. The problem turned out to be the battery. After the initial start, the battery volts/amps?? would drop below the power level that the computer was looking for to fire off the injectors (I think it was 13.8 volts/amps?????) The battery would drop just below this power level but the starter still sounded normal. When it was in this condition, my buddy hooked up the battery charger to help boost the power level and it would start right up. A new battery fixed my issues. I hope this helps. Good luck.

Dennis

 

[tonylong]

Good thought, battery. My symptoms are similar, but the failure to start only happened once so no clear pattern yet.
But ,,, the battery is easy to check. Even though I still suspect bad fuel, there's no fuel smell when it cranks but won't run. It does kinda seem like no injectors are squirting. I don't wanna drive it far from home because getting it towed scares me. The one time it failed to start it was only about 3/4 mile so I walked home and got the Jeep, then later when it did start (now cold) I just drove home and walked back to get the Jeep (downhill this time, whew).

I hope I can find a clear problem rather than some intermittent quirk.

 

[tonylong]

Aha there does seem to be a problem with the battery. Checked the fluid level last night, found it half dry. Put water in and hooked it up to the charger overnight.
Checked it this am, it showed about 3/4 charged.
Mechanic says batt is probably fried. He's gonna check the charging out, maybe it was overcharging and boiled it out.
We'll see the outcome.

 

[bill5674]

did you check spark and fuel yet?ok battery might be showing less than 100%,but if it spins fast enough thats all that matters.kind of like saying it is a quart low,not to spec so that might be it.not trying to be a wise butt, but ? start with the basics....bill

 

[tonylong]

Sadly she's starting just fine now. I'm gonna have the mechanic check it out. I don't have the means to check the fuel, and I can't be risking having her crap on me when I'm very far from home. The nearest other towns are 7+ miles away and all down the mountain. I'd never be able to walk home, there's no cabs around here either. My choices are either drive myself, or walk.

 

[onedef92]

Check your coil and ignition control module, too. My coil died without warning, taking my ICM out with it, resulting in the crank, no-start condition you're describing.

 

[tonylong]

Update. She starts when cold, but runs rough and stumbles. I replaced the plugs, they were somewhat dirty, and replaced the batt, too. It's charging at 14.2 V.
I still can't gtrust her to not leave me stranded someplace.
Next is to check the fuel filter, and pressure. This all started when I filled with Hess Premium, she never liked Hess much and always ran rough on it. Plan A is to eliminate bad fuel as the problem. Plan B, still working on that.

 

[tonylong]

OK Update.
Will start when cold, but runs rough and surges sometimes.
Won't restart when warmed up even a little.
Mechanic checked fuel pressure - 36-42.
Ignition OK, butr replaced all plugs anyway, old ones 2 years old, kinda cruddy looking.
Removed all fuel - looked clean but smells odd. Mechanic thinks too much ethanol in it. replaced with good fuel.
No change in performance.
Pulled wires from up to 4 injectors - no change. Hmmm.
Next steps are to compression check 1 or 2 cylinders.
then remove and inspect/flush injectors.

Any suggestions more than welcome.

Also ... anyone know how to check fuel quality?
Are there standards that can be verified?

Note - this car never gave me any trouble at all in running before the Hess fill up.

 

[bill5674]

tony, when hot and you get a no start,do you have spark? if so you might want to unplug each side injectors one side at a time.i believe they fire all right bank then all left bank.poss high Resistance in one or more when hot might give you a no start.don`t waste time checking one or two cylinders for compression either all of them or dont bother.besides i doubt very much that low compression is your trouble.

 

[91 Black Convertible]

...you might want to unplug each side injectors one side at a time.i believe they fire all right bank then all left bank.

I thought I read recently, either in this forum or one of the others, that all 8 injectors fire at once, not right bank, left bank as many of us thought previously. :confused

Can someone confirm this?

Jim S.