i recently bought an 88 bronco with a 302 when i bought the truck it ran just fine.. but all of a sudden it doesn't want to start.. it has spark and i have replaced the rear fuel pump and both fuel pumps are running when i turn the ignition on. in the process of these issues i have also replaced the fuel filter, the distributor cap, distributor, ignition module, distributor plug, plugs and wires, and the coil. any ideas?

 

You say it turns and tries to start? what does it do? backfires then die? only turns? i'm guessing fuel issues here, change the fuel filter and refill the tank with fresh fuel, get a fuel pressure gauge and measure it. Is it carb? check the carburetor also...

Have you checked the relays and fuses? (maxifuses even, if they are the same as mine).

btw... welcome!

 

EFI? Get a pressure gauge and ensure you're getting proper fuel pressure. If you are then it sounds like the injectors aren't firing. That means the brain (ECM) isn't telling the injector to shoot.

I'd be checking for codes, go buy a cheapy ODB I scanner (Innova 3145) and see if it's throwing any codes. There won't be many since it just has a few sensors but that may give you a start.

Did you do any big electrical mod's? Gianormous amp or do any welding??? Could be you zorched the ECM (computer) also something to check. If it is the ECM they're out there for about $100.00. I've never tried to use a wrecking yard brain... If you can find an exact match may be a source too.

 

If its EFI, maybe inertia shut off switch??

 

Need more information, like what do you mean but "doesn't start". Does it crank? Why did you replace both pumps? Your truck is EFI, did you check the fuel pressure? If you have good fuel pressure are you sure the injectors are firing? You can check them with a noid light.

I would ignore this post except for the first sentence asking you to check the fuel pressure. Replacing the computer should be the very last check.

He wouldn't be hearing the pumps run if the inertia switch was tripped.

 

Andy... Instead of telling everyone to ignore my post perhaps you can explain why and give a better one. I'd like to know what's wrong with it.... Maybe you can share some vast wisdom here.

 

OK....

First, you didn't say what proper fuel pressure is. For an 88 302, it's 35 PSI. Even he does have the proper pressure, it could be any one of a hundred different problems. Diagnosing it as "the injectors aren't firing" is premature without more information.

There are 100's of possible trouble codes from the ECM. Most problems that I have read about in this forum are pointed to by the codes.

Here you are talking about replacing the computer, which it's WAY too early to even suggest. PCM's rarely go bad and to start talking about it this early in the troubleshooting process is leading the OP down the wrong road.

I was probably a little harsh when I posted what I did, I will give you that. I'm sorry if I offended you, that is never my intent.

 

this thread is making me miss my carb'd 351

 

JEEEZ USAF Ford Guy I hear you... I thought you had a good suggestion!

Andy, apology accepted HOWEVER... In 35 years of building, refurbishing and repairing fire apparatus (trucks) I've never poo poo'd anyone's suggestions for trouble shooting, even my 16 yo son has come up with valid suggestions. THE FIRST thing we do on an ECM controlled motor that is misbehaving is to run a code scan. You'd be amazed how many times we've been lead out of the forest with a simple scan.

Re-read my post carefully and you'll see that I'm not suggesting that JF replace his ECM I'm suggesting he hook up a scanner to SEE if the ECM is shot. I've personally blown up ECM (PCX EMMS) systems on a Cummins ISC 315 by forgetting to unhook the negative/positive wires before welding. Guess what happened, it wouldn't start. Early ECM's are very susceptible to large doses of ESD (electro static discharge) Hence the question "any welding?"

Now that being said I'm sure Andy wasn't meaning to be snarky, even tho' jumping on others posts is bad form for forums, we're all here to help. I think...

 

My 89 stopped running one day and after tons of looking it was the timing chain. It was firing and was doing everything else it was supposed to it still would not run. The only way I found it was when i took the cap off and moved the crank back and forth with a breaker bar, the crank turned about 20 degrees before the rotor did. When I took it all apart and put a new chain on it the old one had jumped a few teeth and was really stretched. Just a thought.

 

All valid points.

The only thing I can add is that sometimes someone will jump in with bad advice, sometimes horrible advice, or flat-out wrong information.

 

Ol' Greystreak's head is still spinning over this one... relax folks. There is a good reason for any suggestion but before we go off half-cocked about them lets make one or two things clear. EEC-IV codes are the key to diagnosing the problems with an EFI Ford prior to the inception of federally mandated OBD-II computer systems. There is no argument against this, its just simply the truth. Those of us who grew up with carburetors and ignition points and vacuum advance and next-to-no emission equipment, long for a vehicle that was that "simple" to tinker with. But face it, its not gonna happen and unless we are willing to spend some time learning a new method of diagnosis, there is the potential for disastrous repercussions if we apply the old methods to the new technology.

To his credit, hdfe did exactly what I would have suggested to do first. (It goes back to the old school ignition trilogy and you know there is air getting in there and the electrical is the hardest part to diagnose so go with the potential fuel issues first). But to Andym's credit he discredited the idea of skipping a large number of other steps before assuming the PCM had failed. The EEC-IV fault codes can and will save you hundreds of dollars and hours chasing ghosts in the vehicles that are equipped with the ability to generate them.

So, if I may say, girls, you are BOTH pretty! Now lets help jfcook figure out why his Bronco isn't running properly. before we scare him off.

 

You got here in the nick of time, we were just about to come to blows over this one!

 

Oh yeah...make sure there is fuel in your tank.

 

Have you noticed the guy posted once and hasn't answered ever since? (wich means he probably didn't even check this back). I wouldn't bother answering this issue anymore.