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Old 12-12-2012, 08:44 PM   #1
JustinSB
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Bronco Info: '93, 302, Rancho 4" lift, LS diff, 33" Micky Tom Bajas
New ECM, ran briefly, now no spark or fuel

Here is my story:

'93 Bronco with a 5.0 and E40D

A few weeks ago the truck stopped running. The fuel pump was on constantly, no fuel in the cylinders. Was found to be a burnt ECM.

I replaced the ECM, the fuel pump would now prime normally, but when I turned the key to start, nothing happened. I was able to start the truck by running a jumper from the battery to the stater relay. Did this a few times and the truck started and ran fine.

I started the truck via a jumper to the starter relay when put the new computer in. It started fine. Then I bolted the inner fender back in place and started packing up.

When I finally got loaded up and ready to drive home. I went to run a jumper to the starter relay. The engine just turned over but wont start. I have no fuel at the rails (the fuel pumps don't activate) nor do I have any spark.

I checked the output from the coil while the engine in cranking via a jumper to the starter relay and there is nothing coming from the coil. I went to swap the fuel pump relay for the horn relay and found that my horn no longer works either.

I have a thought that maybe the new ECM got fried, but I cant take it apart without violating the warranty on it. So I am not able to check that.

I am pretty frustrated and confused. Where to from here?
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Old 12-12-2012, 09:34 PM   #2
cmartin2112
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Bronco Info: 1990 XLT, 5.8L 351W, K&N intake, Custom exhuast, 4" RC Lift, 33" Dick Cepek FC-II tires
I could be wrong here but have you checked that the CPS is working properly?
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Old 12-12-2012, 10:51 PM   #3
JustinSB
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I have not checked the CPS. Here is an update:

I unbolted the fuse box and the truck is now running again. I think some of the wires into/out of the box got pinched when I re-installed the inner fender.

However I took it for a drive on the freeway and the speedometer doesn't work, the ABS light is on, and the transmission wont shift higher than 2nd gear (it was revving out at 25 mph and I only felt one shift).

I would think that the transmission issue is due to the ECM. I bought an ECM from a company who asked for my vehicle info and VIN to program the ECM. Would it be a possible mistake that they made in programming the ECM?
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Old 12-13-2012, 06:41 PM   #4
JustinSB
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Update:

I spent all afternoon chasing why the horn didn't work. My hope was that the horn was related to the ABS, speedo, and trans problems. After finding continuity between the horn switch and the relay, I grounded the horn switch with a jumper to the negative battery terminal and the horn worked. I then re installed the horn and found that it worked.

The truck then started and drove fine.

I am lead to believe that all the problems I was having were due to some of the firewall connectors getting pulled on when I moved the inner fender to install the ECM. While chasing the horn issue, I pulled and re installed all the connectors on the wiring harness. I am thinking that solved the problem.

I am not 100% confident that the problem is solved. I am going to bring up a flatbed and trailer my truck home before I start driving it again.
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