Jretal

you guys hear of this?

So our friend (and mechanic) has had the UrQ for the past month trying to help us figure out the mis-firing we were having. He found and fixed the following issues (half of which I should have done myself but didn't think of it):

- Plugs
- Rotor
- Cap
- cleaned #2 injector (wasn't spraying, only dribbling)
- verified wires were good

He tested the IAT, which was fine, verified all the switches, etc were working properly, and overall got the car running a LOT better than it was (amazing what how much a basic tuneup works <bangs head on desk>).

Unfortunately, we still have a slight misfire. He had a read that if you hardwire the fuel pump, it can blow a transistor in the ECU which will cause the car to stumble. He thinks this is the issue.

With that said, it's very possible the PO caused this problem. The FP is hardwired in w/ a relay and an on/off switch, and stays on all the time when you turn the key (no prime and shut off if you just turn the key but dont' start the car). I don't think this is right, correct? I know how the 4000s would prime then shut off, but not sure w/ the UrQ as I haven't been around one that's been unmolested.

Other than seeing that the pump was relayed, I never bothered to check exactly HOW it was wired. B/c the pump stays on at all times, I'm figuring that they used an ignition trigger to turn the pump on instead of the existing power line, and then put a switch in there to shut the pump off when not in use.

So have any of you heard of this issue? Really appreciate the help. I'm going see if my dad can double check to see how they wired the relay under the seat, but otherwise I guess I'm going to be looking for a used UrQ ECU to test and see if this truely is the issue.

So if you got one kicking around that I can borrow or buy for cheap, please let me know

Thanks all!

ralleyquattro

Yes, my first Ur-q had a hardwired pump and non functioning fuel FV as well... yep, blown transistor in the ECU.

In case you need one I have couple of spare MAC02s

Cheers

4x5x5

I'd be interested in hearing more on this. How does the ECU/transistor know the difference an after market relay and the proper relay for the fuel pump? Assuming the add on bypassed the proper relay, how the did transistor blow with no power to it? Not idle questions per se as I have my FP wired this way (10+years) , but then I do not have a fuel FV but I do have a MAC 02 currently residing where my MAC 01 usually does.
Mike

Katman

ECU can't tell if the FPump transistor is gone (well, other then the motor wouldn't start!). You'd know if the FV transistor went, as mixture would probably be somewhat affectd, and you wouldn't hear the comforting buzz of the FV under the hood..

I'd suspect that it went the other way. Transistor blew, then they did the hardwire as a workaround.

coupeq1983

[QUOTE=I'd suspect that it went the other way. Transistor blew, then they did the hard-wired as a workaround.[/QUOTE]

I would second the motion as above, car may have been running lean causing the FV to work really hard, or simply a defective FV, might do some good to install a in-line fuse on this circuit to prevent the MAC-02 from feeling the brunt of brute force in the engine compartment I.E. chaffed or grounded FV lead. I have a Euro Fuel distributor here, probably run just fine without the FV set up, and USA type metering head. I have no use for this unit as I live in California, all smog laws apply here, and then some....