Afternoon all. Having a bit of an issue with my brother's 1988 Bronco (351W/auto). About a month back, out of the blue, the truck wouldn't start. Cranked just fine, but wouldn't kick over. Prior to that, he had been experiencing some hot-start issues with extended crank times.

We determined it has good fuel pressure (40 psi of prime) and can smell fuel when it's cranking. We DID NOT have spark at the plugs. We found one of those diagnostic trees online and through that determined that we must have had a problem with the PIP. Fast forward to a week ago. My dad rebuilt the distributor with a new PIP and ICM (dist. mounted). Dropped it back in the truck, and we were hoping that it would fire right up. Unfortunately, we're right back to where we started before we pulled the distributor. We're still having an issue with spark.

Now, does anyone have any experience they'd be willing to teach a young'un in regards to diagnosing electrical issues on these old Fords? I have your basic tools (multimeter, test light). Let me know if more info is required. I'd just like to figure out what is causing this issue - mostly so I can get the truck running and OUT of my parking space in the driveway!!

 

We're still having an issue with spark.

Does this mean you have no spark?
Rather than drag this out, if you still have NO spark, remove the spout and see if spark returns. If so it is probably the PCM.. At that point it is advisable to disconnect the battery and pull it out and inspect the capacitors for bulging or leaking and boards for burns etc.

 

Sandy's suggestion is quick and easy. Give that a try.

If that doesn't work, work backwards. Verify that there is no spark coming from the wire to the plug. Verify that the rotor spins when you're cranking. See if the coil is sending power to the cap. See if the coil is getting power. Somewhere in that series, you will find where the disconnect is.

I will end with a problem that I solved personally. I had intermittent spark on an '89 351w. The fine folks here pointed out that the plug that goes into the coil with 2 wire sometimes fails and causes the terminals to become loose and will not be pushed onto the prongs on the coil. This was my issue. When I probed the back side of the plug, it said I had all the power in the world going to the coil, but the power never actually made it into the coil.

Hope this helps.

 

Yes, no spark. I completely forgot about doing that!! Thanks for the tip, Sandy. I'll do that when I get home.

 

Thanks for the input Davey. I can say with certainty there is no spark to the plugs. Will have to do as you suggest and start looking backwards. What do you use to verify power? Test light or multimeter?

 

I use a multimeter. A test light will light up some even with very low voltage and might cover up a problem.

 

If your injectors are firing and your tach is moving when you crank, than your PIP is good. Check your coil, and ICM. Hook a test light up between the negative side of the coil and the positive battery post and crank the engine. If the light flashes, your ICM is good and your coil is probably bad. If it doesn't flash, then your ICM is bad.

 

Guys, I appreciate everyone who was willing to help me out. You all won't believe what the issue turned out to be.......

One of the two wires in the coil plug had actually de-pinned itself from the connector and fell out. BUT, it fell out in such a way that it buried itself under the wiring harness and hid itself there! On first visual inspection nothing looked wrong (unless you knew off the top of your head that plug was supposed to have two wires - I didn't) until I grabbed the harness and shook it around. Then the wire popped up. Jammed it back in the connector and the truck fired right up.

I know. I'm shaking my head at myself just as much as y'all are shaking yours at me.

 

I'd rather be lucky than good any day. Glad you found it.

 

Bingooo. At least it wasn't an expensive repair!

 

Ha! Me too Sandy! Thanks for your suggestion about the spout - can't believe I forgot about that one.

Not at all! New plug and pigtails and we're back to it!

 

Thanks for reporting your repair results.

 

Sure thing. Thanks for not giving me too much flak for the obvious issue that was overlooked!

 

when you fixed the wiring did you place the harness and plug in such a way there is no stress on the connector or wires, so that if your truck vibrates while driving or idling and hit a bump, the wiring is secure and doesnt josttle about? I found that when my cars harness was placed back down by a previous work when the transmission was replaced under warranty, the guy pulled damn near every sensor/injector connector tightly, so much so the TPS had a replaced pig tail years later but the rest were left to be this way. I didnt replace any, but i went through and pulled the connectors away from the wiring harness and made sure each connected without much stress so that they wouldnt get worse.

My 4.9 the connector you speak of could use some adjustment.


I dint like how that small connector is pulling and weighing the wire downward, for example. ( I think you said you have a 302, but i assume the coil connector is the same)

 

Yes, we did. That coil plug (it does look the same) came with a pigtail, and we made sure to leave ample wiring so as not to let what you just described happen here.

Interesting to note - this is the second time a connector has come de-pinned and caused an issue. First it was the alternator, now the coil plug!