Good evening everyone. I am on the 7.3 forum quite a bit but have never posted on the bronco forum. I am trying to get my son's '89 bronco running. It ran fine this summer but has sat for several months. I can get it to start but won't respond to the throttle and will rev up and die. I have checked spark and fuel. When I pump the throttle it will slightly rev and backfire. It has a newer dist.cap, plugs, plug wires, coil. Any suggestions would be appreciated. This is a 302 with a manual tranny. Thanks in advance.
I have not checked fuel pressure. I do not have a pressure gauge where I am. I did disconnect the fuel line on the out side of the filter and it has a large volume. I have been checking connections and general visual of wires for the last 2 hours..
If the Engine Coolant Temperature Sensor (ECT) doesn't tell the PCM that the truck is warmed up the PCM might be telling the engine to flood itself.
The backfire sounds like a timing problem but if there's no work been done then the timing should not have changed that's why I suggested the the wiring might be examined for deficiencies.
It does start and idle? But won't accelerate? Does it warm up? The cooling system is in good shape?
It will start, rev and die in about 2 seconds. It will not idle or run long enough to warm up. I disconnected every connector I could and checked for dielectric grease. I had filled them a couple of years ago. Maybe a condenser?? I am guessing. I have it in my shop now and will start getting serious tomorrow after work.
Good call on the idle speed air control bypass valve. That is one of the first things I will do. I want to check fuel pressure as well. I will pull some of the plugs. I also have another dist cap I will put on. Thanks for your insight.
Update, Fuel pressure is good, iac, egr cleaned, dist cap and rotor is new. Same thing starts revs up and dies. If you pump the throttle it will run with backfiring and erratic rpms until it dies. Plugs are dry, would not appear to be flooding. Not sure what to do next. Self read codes indicate a fuel inertia switch inactive, been this way since we bought it. The previous owner had an alarm and the switch was replaced with a relay. Nothing new for this vehicle. Any suggestions????
Did you consider water in the gasoline? What was the fuel pressure, should be above 35 and below 40. If you jump the fuel pump on the test connector the fuel pump will run continuously without the PCM cutting it off. The fuel pump is the electrical connection on the short arm of the test connector. Turn the key to run and the pump will run continuously. When the pump is turned off the pressure should not drop quickly, that indicates either bad injectors or a bad regulator. Check the return line for flow. there shouldn't be any flow if the pressure does not go to 40 with the engine off, if there is flow suspect fuel regulator. If not suspect fuel injectors.
I appreciate the responses and suggestions. Next step I will drain fuel tank (1/2 full). I have fresh gas at my shop so it is easy enough to address that issue. Needless to say I am frustrated and calling it a night. I will start rechecking everything again tomorrow. Thanks.
Sounds like fuel. When you turn on the key, the pump turns on for a few seconds, then it turns off untill you start. Then it is sappose to turn back on. I suspect it is not and it runs out of gas. A quick way to check this is to have someone spray starter fluid at the intake. If it keeps running, you know its fuel. Maybe the pump, maybe a filter.
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90' Bronco, 351, MSD Ign., SS 3" exhaust,
38" x 15.50 R15 Dirt Grips, 14" x 15" Alcoa wheels
6" lift w/ cutout flares, 40 gal. fuel tank
F diff - lockright locker, 4.88's
R diff - Powertrax locker, 4.88's
Cast diff cover w/ carrier braces
Rear full float axles, truss, Above spring traction bars
Sounds like fuel. When you turn on the key, the pump turns on for a few seconds, then it turns off untill you start. Then it is sappose to turn back on. I suspect it is not and it runs out of gas. A quick way to check this is to have someone spray starter fluid at the intake. If it keeps running, you know its fuel. Maybe the pump, maybe a filter.
I did spray starting fluid in the plenum, its response led me to replacing the high pressure pump and filter. I thought the pressure was a little low, something like 29psi. Have great pressure now but problem persists.
When I picked up my 90 a few months ago it had been sitting for awhile, it ran enough to get it home but that was about it, I drained and refilled the tank and added a can of seafoam to the tank, plus ran some through the intake, (vaccum line) runs great.
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