Hi, I have an 87 F-250, 7.5l, carb,w/4spd new era trans. I had an issue with the ignition system shutting down (no spark) at the most inappropriate times. Upon my troubleshooting/repair of the problem, I have replaced the starter relay, ign coil,ign wires,cap, rotor, distributor,ign. switch on column, Duraspark module. Also ran external grounds from dist. to block, verified power to ign module during run and start phase (red and white wire). Now I have spark during the run position but not during the crank phase. I have also checked every possible position of the ign switch on the column. I love this truck!!
PLEASE HELP ME!! for I am lost

 

Well.....I noticed alot of people looked at my question/problem, with no replies/answers, after a total re-diagnostic(by myself I might add) it turned out the Hall Effect coil in the new distributor was faulty. After digging up the reciept and exchanging it. I poppped the replacement in and at the first bump of the key she fired right up! A quick shot with the timing light and I was good to go. Dunno if I had everyone stumped or what, but I figured I'd post the fix just in case anyone else comes across this issue.

 

At least you had sense enough to question the quality of a new part. Good looking out.
On the bright side, you gained a lot of troubleshooting experience and got to spend some quality 1 on 1 time with your truck.

Thanks for posting the fix.


Dave

 

This part had me stumped.
So rather than opening my 'mouth' and proving i'm ignorant, I figured I'd watch and see what I could learn.

Did you try and troubleshoot this at first? Or did you just say f it and replace the entire ignition system, thinking that that would have to fix it?
I know I have done that in a fit of frustration and desperation.
I guess I'm lucky I did not get a 'bad' new part.

Thank you for sharing what you've learned. I'm glad to hear you have resolved your issue.

 

just to clarify the the stump factor in the quote; when I turned the key to the crank position the engine would not fire (no spark), upon releasing the key the engine would recieve spark and act as if it wanted to run. As far as the position of the ignition switch, I meant the electrical switch mounted on the column that the rod actuates, which has slots for the mounting, enabling adjustment of it's position. Also....now this is the part that's evading me again...the original problem has returned (truck shuts down after approx. 1/2 to 1 hr of driving) I wait for about 5 to ten minutes then i can continue for usually a shorter distance than before. it has dual tanks and the fuel line routing is stock so i've ruled out vapor lock. and as previously stated, all ignition related components are new. I only use the rear tank and the switch in the dash appears to test ok. I'm eyeballing the cutting torch and visualizing my truck as handy little 5x5 squares at this point.

 

Oh man, don't do that...


From your symptom of it running for a while and then dying, it sounds like an electrical component is failing after heating up. Either the coil or the module. The spark when you let the key off also sounds like a capacitor discharging. Do you have an ohmmeter?
It's easy to check the coil and you might throw it in the oven and see if it doesn't go open or low ohms.

Just somewhere to start.

I keep a spare Duraspark box under my front seat. Mine seems to blow every 80k or so.

I don't think it's a fuel problem at all if you have a mechanical pump. It could be a failing intank pump if you have the 'hot fueling' system, but I don't see it.

 

I noticed that there is a TSB on the the Duraspark mounting to the fender well, it seems the box is grounded thru the three mounting bolts..problem with that is...my fender well is plastic....should I run a seperate ground from the module to the eng block? And yes it has a electric fuel pmp in the tank. Awhile ago I replaced the sending unit assembly in the tank but re-used the existing fuel pmp. I've checked and re-checked the harness and plug to the sending unit and all is good....Yes I have an Automotive multi tester and will retest the coil as you described.(wouldn't that be a hoot if that was a bad new part also?) I have the original Duraspark module that displays the same exact symptoms so my questioning the module again seems kinda redundant

 

Mine (Duraspark) has never been grounded, and it works. ?!?
Couldn't hurt to try a ground, there's one up on the wiper motor.

Well like you said you've replaced everything, I don't know where to tell you to start.
It might be nice to see if the next time it dies you plug in the old spark box and see if it fires right up.
In my experience when they fail I get one huge backfire and they're done. If I'm driving along and that happens I just plug it in and drive away with it sitting in there not even attached to the fender.

 

I don't get the backfire just a I'm gonna shut down and let that semi behind you slam into your rear end kinda deal. I need to take a trip today so i'll bring the old module with me...see what happens. Reminds me of my old Harley days where a support truck with parts has to follow me where ever I go...lol....just out of curiosity..could I eliminate the electric in tank fuel pump and use a mechanical...when I replaced the timing chain I noticed the eccentric lobe part was there so it would run a mech. pump.....or is it too far from the tank (all the way to the rear) for it to pull fuel from?

 

Mine does.
I have nothing but a hose and a sender in the tank.

You have a blankoff plate on your timing case?
You'd have to make sure it (the pump) would clear your oilfilter.
Do you have the right angle filter adapter?

I don't get the "backfire-Semi" thing.....
I DO know about having a support vehicle

 

Oh, I reread it, I understand...

 

I also went back and read the thread.

In my mind..... (?!?)
If you were loosing the pump it would act like you were running out of gas, not just shut off suddenly.

 

yes there is a blankoff plate and yes it has the right angle filter adapter, I eliminated the oil cooler set up because the cooling core leaked and capped off the hose ports. I was going to get rid of the adapter also but the crossmember would not allow a filter to come directly off the block. I'm sure I could reposition the adapter to clear the fuel pump.As far as the backfire-semi thing...just an attempt at humor.

 

I had the same feeling...but hey, I reaching for a conclusion at this point....makes me feel like I'm accomplishing something.....lol

 

Have you changed the fuel filter ??