My 89 full size bronco has been acting up recently, it's a 5.0 aod and ran strong until a few months ago. I guess I'll start with the issues I have been having up until now. Back in may I wasnt driving it so the only issues I noticed was a hunting idle and bogging out badly from the get-go until it stopped running altogether. I did some testing a found that the fuel pump had gone on me. couldn't hear it at all, so for good insurance I replaced both, she started back up and still same issues as before it died. so I said screw it and let her sit until September when I put a temp on it to move it out of the yard and also see what other problems I was having with it. before I go on I should mention that in may I pulled a code 67 for nutral safety switch I believe. It's now since gone away but when I put temp insurance on it I pulled a code 63. if I remember correctly that's throttle position voltage low or something like that and that is still there. anyways while driving it around for a few days I noticed that it's terrible on gas, puffs black smoke as much as a diesel, bad shifts into whatever gear. still has the hunting idle and a few more symptoms that all point to a bad throttle position sensor but she started every single time and wouldn't stall out at long as a revved it up for a minute or so. Anyways on Thursday the one time I tried to pull out before revving it up she stalled out in the back lane and would not start back up. I had nothing or nobody to help push it back in the yard it was late so I let it sit over night and boy did I **** a few people off. So yesterday I got it back in the yard and did some testing I do have spark although I don't know if it's timed right yet, I also noticed that I can hear the pumps loud and clear but when you push in the valve on the fuel rail nothing comes out but while cranking it shoots out a few feet is this normal? yes I did test the fuel pressure regulator a few months ago by pulling the vacuum line and it all seems good and no I do not have a gauge to see what kind of psi I'm getting. a few other things I thought I would mention are that I replaced the o2 and intake air temp sensors about a year and a half ago. Today I was doing some reading and found that the pcm could be at fault, is this likely? Either way I'm going to pull it out and look at it tomorrow. so I guess my questions are could a tps cause a no start condition, is there something wrong with my fuel system, could the pcm be at fault, and most important WHY ISNT MY TRUCK RUNNING!?!?another funny thing is that all these problems started after I put a muffler and tailpipe on it lol I ran it for like 2 years with it cut of at the before the cat. I haven't had much time to look at it yet but I'll do some digging tomorrow. has anyone else had these similar issues? just thought I would ask before I start spending time and money on it, any input is helpful at this point.

 

All I'm hearing is crickets here..... someone has to of had similar issues before.

 

When you put together running sentences it's hard to follow the story.

You have a Code 63, TPS output too low or has intermittently gone too low. We need to know when the code was displayed.

Poor mileage and black smoke mean the engine is running rich. You need to rent a fuel pressure tester.

Do the pumps run all the time when you turn the ignition switch from Off to Run? If they do that is a classic symptom of a failed computer.

Either way pull the computer out then inspect it.

 

I posted this on my phone and could not for the life of me figure out how to make a new paragraph, I apologize about that. I got code 63 shortly after putting a battery in it so around September and it has not gone away since. as for the fuel pumps they both run for the normal 2 seconds and sound very strong. I pulled the pcm today, the caps and everything else inside look fine and all connections look good. I know these symptoms point to a bad tps, but can that cause a no start?

 

There are two parts to a code check. The first are any codes displayed from the Key On Engine Off (KOEO) tests. If there are no errors the System Pass code 11 will be displayed (twice). After that a single separator flash is displayed then any stored codes from Continuous Memory are flashed out. If no stored codes, System Pass code 11 is once again displayed (twice).

So it's important to know when the code was displayed. If KOEO that means the TPS output is too low all the time. If it is in CM, the TPS output was intermittently low.

Can a bad TPS cause a no start condition? It's possible. If the computer senses Wide Open Throttle (WOT) during cranking (=>4.5 VDC) it will keep the injectors turned off.

A simple test is to disconnect the TPS, then try cranking. If it starts, you know it's a bad TPS, although the code you are getting is showing the exact opposite....

If that does not help, you can try squirting a little bit of starting fluid in the intake, then crank. If the engines starts then you have a fuel pressure problem.

 

I tried starting fluid a few days back, it didn't do anything. The code is always displayed, engine running or not. I'll try unplugging it and see what happens.

 

OK so unplugging the tps did nothing. However I ran codes once again, I don't know if it's because I took out the pcm yesterday, but ta-da more codes. I got codes 21, 63, and 24.

 

Codes 21,24 are triggered by not warming up the truck before running the KOEO tests.

Code 21: ECT out of self test range 0.3 to 3.7 volts.

Code 24: ACT sensor out of self test range 0.3 to 3.7 volts.


If the truck will not start with some starting fluid, you have a spark problem.

 

where should I start with that? I am getting spark, I just haven't had the time to see if it's timed right yet. I'm assuming that if something was wrong with the tfi module it would throw a code? I'm sorry these efi engines haven't really given me much trouble before.

 

Where are you getting spark? Output of the coil, at a spark plug?

If you are getting spark at a plug, pull the SPOUT, then crank the engine with a timing light on cylinder#1. Verify the timing is ~ 10 BTDC.


I'm assuming that if something was wrong with the tfi module it would throw a code? No

 

the TFI wont throw codes. since the rig has sat for awhile have you check the condition of the cap/rotor? those are cheap items to get replaced and rule out. Pull a few spark plugs and see what they look like, this could also give us some ideas. did you replace the fuel filter?

 

One of the first things I did was put the new cap/rotor from my mustang on, still nothing. the plugs are motorcraft with not even 2000 km's and seemed to be fine. as for the fuel filter I kid you not my truck does not have one. all the lines look factory to me, I followed the lines about a million times over from tank to rail when I did the pump and there is nothing. I do have the canister thing for going up hill but that's it, however I can't seem to find a new filter for it at the parts stores. I have the day off tomorrow so I'll do some more digging then.

 

Not all fuel reservoirs contain a filter. If there is no specific markings then your "might" have one.

More info from Steve83:


88 Single-Function Reservoir

Used on '88-89 Broncos & F-series/E-series/Rangers/others with single tank dual-pump EFI. In this version, the only moving part is the tank-side inlet check valve. The return ports flow freely and are NOT connected to the reservoir. The engine-side supply port is open to the reservoir.

To test it, unplug the frame fuel pump, disconnect the engine-side supply (large) line, and cycle the key. If fuel flows out of the reservoir nipple, the reservoir is working normally. If not, disconnect the tank-side supply (large) line, and cycle the key. If fuel flows out of the line, the reservoir check valve is probably stuck, or its internal filter is clogged.

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862, or equivalent filter.







IMHO it's kind of a moot point since the truck will not fire with some starting fluid.

 

wow, my 88 bronco with a 5.0 had a fuel filter located under the driver seat on the inside frame rail.

 

OK, not much of an update here I still haven't had time to push her in the garage yet, however I did look a few things over. first off there isn't much play in the timing chain. I put a breaker bar on the crank pulley and spun it until the rotor turned, there was only about 20 or so degrees of play on the bar. not very much in my opinion for 275000km. I still haven't hooked up ye olde timing light, but the rotor is pointing to #1 at tdc. I also got around to doing a compression test, obviously on a cold engine without using oil. I got readings of 157-160 and all cylinders with no outliers, amazing in my opinion! keep in mind I'm only the third owner and it was babied until i got the keys to it. I haven't found any broken or melted wires yet however I haven't gone through every wire. it's supposed to be a bit warmer here in the great white north for a few days so I'll bust out the multimeter and see what more I can find.