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Old June 25th, 2010, 09:44 AM
Frank84
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Frank Battersby
95 D90
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ECU swap

I'm having trouble with my '89 classic and decided to try swapping the ECU from my '95 D90 into it. My question is - should it run?

Here's some background. I decided to relocate my classic's ECU and relays to under the dash instead of under the passenger seat so it wouldn't get wet. Seemed easy enough, in fact, too easy. There is plenty of length in the wires and I didn't even have to undo any connections. 30 minute job if you are slow like me.

Now it won't start. I confirmed spark and it cranks strong. There is no power getting to the fuel pump nor the fuel pump fuse (and fuse is good and swapped it anyway). I thought that maybe the ECU case was supposed to be grounded so I ran a jumper from the negative terminal to the case and no luck there. I swapped fuel pump and fuel injection relays with spares too. I looked around for a wire that might have broken and didn't find anything though I really was pretty gentle with everything.

Also, should the fuel pump and fuel pump fuse have power when the key is in the on position or only if I'm cranking it?
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  #2  
Old June 25th, 2010, 10:40 AM
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Turbofan
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Ethan
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I'd start by checking power for the relay at the ecu. If the ecu is powering out like it should, you know your problem is between there and the relay. Don't know about compatibility of the ecu's though.
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Old June 25th, 2010, 12:10 PM
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Chris Davis
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I have used my 14CUX in my 13CU '88 rangie and it works fine. Yes, the swap you are talking about should work. You can also short across the pins on the fuel pump relay to force it on to check the pump/relay. Either the ignition relay and/or the fuel pump relay may have gone bad or one of the pins on those relays when you moved it may pull out. I would start by taking out both relays and looking at the pins and making sure they are fully seated and then I would swap out the relays for known good ones--rule out the easy stuff first.
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  #4  
Old June 25th, 2010, 01:57 PM
Frank84
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Frank Battersby
95 D90
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Thanks for the suggestions and ECU confirmation. I'll try some things tonight. Had a weekend of four wheeling planned so i may be a passenger but I have my fingers crossed!

I tried some spare relays from a parts truck I had a while back, but I guess I don't know for certain that they are still good. Where are the fuel pump and ignition relays on the '95 D90? I found some large fuses under the intake but no relays. I'll try using the D90 ones to swap if I can find them since I know they are good.

EDIT - found the relays
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