I recently bought an '86 F-100 with the fuel injected 302. I plan to use the engine in a future project, but for now I need to use the truck for basic transportation. When I bought the truck, I was told the fuel pump needed to be replaced, and that someone had stolen the distributor cap, rotor and coil. I replaced all this, yet the truck still wouldn't start.

I checked to be sure the fuel pump was delivering fuel at the apropriate pressure, checked to make sure plugs were getting spark, and everything checked out to be good. In desperation, I poured gas into the throttle, and turned the key to be rewarded with the truck roaring to life and running very well, if rich, for as long as the fuel I poured in lasted. Once the fuel I poured into the throttle was used up, the truck, of course, died.

I then bought a Noid light and checked to be sure the injectors were getting power. Bingo- that was definately the end result of the problem.

Now, on to my question: I have been told that the pickup coil (What Chilton's calls the Stator) under the distributor cap is what sends the signals to the injectors to let loose with a squirt of gas, and that if I'm not getting signal to my injectors, that's the most likely culprit. Other sources say there's a cam or crank position sensor that actually does this. I definately don't want to press the shaft gear off the distributor to change out a stator if that's not very likely to be what's wrong. Also, if that is likely the main problem, but there are other possibilities, I would be very interested in knowing about it. Any help here?

 

Welcome to FTE!
All the distributor does is gives the computer a signal for the spark. There should be a crank position sensor as well, and this very well may be the problem. Also, look at the battery leads. There should be the main lead going to the negative terminal, and a smaller wire as well. If the smaller wire isn't hooked up, that means your computer isn't grounded, and can't fire the injectors.

 

Thanks. That's about the most straight-forward answer I've got so far. I've been told everything from "Ya need to replace yer fuel filter thingy," which was one of the FIRST things I did when I bought the truck, to "There ain't nothin that tells an injector when to fire! They spray full time!" which I know better than to believe. Believe it or not, these lines were coming from guys that were working behind the counter of reputable parts stores.

 

By the way, other than the obvious answer of "around the crank," where would this crank position sensor actually be located?

 

On the right (passenger) side, at about 10 o'clock is the sensor itself. It should be a good sized white plastic body, so if you pressure wash the engine, you will see it.

 

Thanks... that's a big help. The truck is actually about 40 miles from where I am now, so I have to wait until my days off to work on it. I'll let ya know how it goes.

 

The injectors fire off of the module as does the fuel pump. If the ECM doesn't see a stator trigger for about 3 seconds, it kills the fuel pump relay. I have never seen a crank sensor on a 302EFI. The old EEC-III has crank triggered ignition. It was non adjustable and not very good. This was back around 1980. I had a LTD with a 351W VV carb and crank triggered ignition. The injectors are batch fired by the ECM seeing trigger from the pick-up coil in the dizzy.
Jimmy

 

If that's the case, then my stator is in good shape. The fuel pump fires every time I turn the engine over. I know because I was using the starter to build up fuel pressure and then using the valve on the fuel rail to bleed out air. Fuel pressure is there. Spark is there. Everything is there, except the signal to the injectors.

That rules out the stator. The ECM is obviously working also, if it also controls the fuel pump. I dumped gasoline into the throttle and it started and ran until all the gas had evaporated. Everything but the EFI system is working.

 

It possibly could be a bad ECM not sending the signal to the injectors if the wiring is all hooked up and correct.
Jimmy

 

Just thought I'd reply to this. Turned out there was a bad relay under the hood. I was lucky enough to run across an ex FoMoCo dealer mechanic who said they used to get these problems in his shop all the time, and nine times out of ten replacing that relay turned the trick. In my case, it just turned out to be a case of corrosion on the contacts. Cleaned them up a little, hooked up the noid light, turned the key, and that little light blinked like a strobe.

 

Gald to hear that you got it figured it out.
Jimmy