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My neighbor bought a camper about a year ago. It is an 86 E350 chassis with a 7.5 L V8....The previous owner bought it with a holley pro-jection 4DI system already installed. One time since owning it, it failed to start and my neighbor remembered not hearing the pump running. He looked out under the hood and wiggled wires and then it started..He didn't have any trouble until a couple weeks ago, it died on him in front of his house. He asked me to take a look at it. I downloaded the install manual and looked at what he had. Wiring under the hood was really poor. The wire from the pump relay down to the pump was running along not tied up, not covered, etc. There were two fuse holders tapped into the battery positive and one was completely melted. There was lots of wiring under the hood like this....Here is what I did and what I have found:
I made a new battery cable to run from bat pos to his starter solenoid. I made it from 2 ga cable. Off of the solenoid at that connection I connected with an eyelet and ran 10 ga wire to a 4 fuse, fuseblock that I mounted near the battery and the pump relay and ECU relay. One feed from the fuse block runs to the red wire for the holley system. (12 volt battery feed). I insulated and secured the fuel pump wire from the relay down to the pump on the frame rail. I replaced the ground lug for the holley system and connected direct to battery neg (ground for the system). If I connect power to the pump wire directly, the electric pump will run and supply fuel to the throttle body, but normal key on, will not make the pump run. The manual also states that there is a red/white wire for the holley that has to go to 12 ign switched source (they call out pos coil as point of connection). I checked this and it is getting 12v with key on. They also call out to connect the loose yellow wire to the neg coil for the pulse as a tach feed (no tach on the truck)....I connected my test light to bat pos and with crank, I get the pulse there. So according to the install guide all of the loose wire connections are there and correct as they should be. With key on, I get no pump run and when cranking I get no injector fuel...no start.
Yesterday at one point, I did get the thing to start and run, but it would only keep running if I jumped direct to the pump feed at the relay. I checked both relays and the ECU relay, gets power to 2 of the 4 terminals and that clicks the relay and powers the 4th terminal. With key on, the pump relay has 12v at three terminals but not the fuel pump feed. That told me, the relay is not operating. I went and purchased two new relays and they both do the same thing. No 4th lug powering. No pump run. At that point is where I jumped 12v to the pump and it began to run. I went in and cranked it and it started and ran rough for a while until it warmed up. We looked all over to insure there were no open vacuum lines (tons of things disconnected and plugged on this thing)...it seemed to run decent after that and after 20 minutes, I shut it off. 30 seconds later I attempted to start and again had no fuel at the injectors and no pump run (jumper removed). I jumped to power pump and it ran, but still no start, no injector fuel....no start...
When you turn the key off, you get a short spray of fuel at the injectors, but no fuel during crank. Install guide says you should get 3-5 second of pump run upon key on. After that, if no pulse detected from coil, pump stops. If during that 3-5 seconds of key on, it starts, then the pump will keep running. I get no pump run on key on or crank. From what I see, the ECU is bad and not turning on the injectors. We have no software to connect a computer to the ECU to look at anything. I hate to condem an ECU without being able to 100% rule everything else out. Everything that should be connected, is connected and getting power/ground/pulse as it should...
I would look a little closer at the relays. Are they the typical bosch style (ie 85 and 86 are the coil, 30 is the switch and 87/87a are the poles?
If that's the case, I would start by verifying the positive power legs are on 86. This rarely makes a difference, but it's a simple place to start. Then ground your neg probe on your dmm and pos on 86. If you get 12v when you turn the key on, then you have power coming. Remember this voltage. Next check pole 85 and it should have very close voltage, less than 1v voltage drop hopefully. 87 should have your battery voltage and 30 should go to your pump. Check both of these leads for voltage drop the same way.
Watch these for timing too, this should point you to either the trigger (ECM) or down stream towards the pump.
It wouldn't hurt to check all the wiring too, including the grounds. Shoddy workmanship could be the whole thing or it could also be a ground issue.
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