I have not started the Bronco in a while. I was saving it for my son to drive when he comes of age. Pulled off the cover the other day, tried to start it and it would not fire. The plugs are new, the wires new, distributor new, new coil and battery and fresh gas. Fuel is getting to the injectors, pump sounds like it is priming fine, but for the first time ever, she cranks and cranks and cranks and simply will not fire. I have not yet checked the fuel pressure to see if the pump is 100%... someone mentioned the injectors could be clogged - seemed a stretch that all would be clogged. Another guy said that when one injector goes down, the computer shuts them all down?? Does anyone have any suggestions of what direction we should head in? Thank you
Will not fire on 1992 Ford Bronco
by Lakeville in East Taunton, MA on May 23, 2010
2 answers 6 comments
ANSWER by Bret Bodas on May 23, 2010
Have you verified the injectors are operating and the spark plugs are firing?
I would see that you have proper injector operation. They normally get power via a relay then are grounded by the engine module. You may want to look at a wiring diagram to determine exactly how the injector circuit operates. You can get a really good diagram here for a good price: http://bit.ly/mitchell_repair_manuals_online
An injector is a type of valve, think of it like an electric garden hose nozzle. When you have 12 volts to the power side and have a good ground the nozzle opens and allows fuel to spray out of the injector. The injector should have 12 volts and it is triggered by the engine module providing a ground to the circuit. They're not likely to all get stuck, so I suspect they're not getting power or the ground signal
COMMENT by Lakeville on May 30, 2010
I'm going nuts now... 1) I have spark - I grounded a spark plug while firing and got an orange spark. 2) I have fuel pressure - I bought a tester and it shows 40# at ignition and holds 36# - 37# steady. 3) I tested the injector wires with a NIOD and got a steady pulsing light. 4) So I changed the fuel injectors (because that had to be the final answer...) The Bronco still will not fire, will not even try for a split second. Is it possible that I somwhow installed the injectors wrong? It seemed pretty simple... Could I possibly have a clogged exhaust that would keep it from trying to fire? With everything present, (confirmed spark, fuel pressure, pulse at the injectors) could the computer be bad somehow? Please help...
ANSWER by dandd on May 23, 2010
Start with the basics, i.e. check for spark at the plugs. When you crank that truck, do you have a nice yellow-blue snapping spark that will jump at least 1/2 inch? Just because the parts are new, does not mean you have spark, i.e there is an ignition module etc. Secondly, after you PROVE that you have spark, spray some fuel or carb cleaner into the throttle body and see if the engine wants to fire? If it does, then yo have a fuel delivery issue. These are 2 first basic steps I perform when I check for a crank/no start.
Thank you for the quick responses. I have verified spark. I have also verified that I have fuel getting to the injectors. We stuck a knife in the injector test port while cranking the vehicle and fuel shot out at a pretty good rate. We did not have a guage with us, so we did not check the pressure. The pump pressure was mentioned as a possibility by a friend over the phone. He said that just because there was pressure, did not mean that there was enough pressure. I'll try the starter fluid when I get home this afternoon. I should also be able to check the pressure. Thanks. I will post again with my findings.
OK - I have nice pressure from the fuel pump. It goes up to 40 and then settles nicely at 30. I sprayed carb cleaner and she tried for a second or two and that was that. Sounds like Bretb is on top of the problem. Seems like my injectors are the issue. And I will admit that I am in denial because I am not a mechanic and the injectors will be all new for me. I can build a ten story building with my eyes closed, but gears are not my specialty. I read something about injectors getting stuck or frozen because of sitting for a long time. There was something about piercing the white wire and tapping a ground to "unstick" them. I'm going to find a wiring diagram per the suggestion. Is there any other advise that anyone can lend me? Any assistance will be much appreciated.
COMMENT by Lakeville on May 26, 2010
OK - I got a NOID and tested the injector wires. On everyone I could reach without removing anything, I got a nice steady pulse. So with everything that I have to date - cranking power, verified spark, good pump pressure, and a pulsing noid, I must assume that the length of time between attempted start-ups has clogged the injectors. So this weekend, I will attempt to remove the plenum, the injector rail and replace the injectors. If anyone has any further advise with what lies ahead, I would greatly appreciate it. This will be my first attempt at such a repair. Thank you once again.
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