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Discussion Starter · #1 ·
I bought a 1993 Mazda MX6 that had been sitting awhile....here is her story.

She broke down on the previous owner and they were to have bought a new distributor for 800.00 (shop said) and had it put in. They got it back from the shop and ran for three weeks. Then the people that put the distributor in seemed to run an ignition module (screwed to fender) and wired into the distributor (weird). The car ran for another three weeks and stopped and they just parked it.

I came along after seeing the car in the junk yard with others..."DAMN" I can't believe that car is in here. Talked to the junk yard and wouldn't sell it because it belonged to a customer who wanted it repaired. Got into the car and got the registration and long story short, bought the car from the man for little money and paid his towing bill to the yard.

Now, I have taken all the wired crap off the distributor and replaced the distributor and she cranks and cranks so well that it almost wants to start..., I can even feel the exhaust manifolds and they are warm from all the cranking...then I notice that the fuel pump is not making any sounds at all as I place my ear to the tank inlet.

Removed the tank and the pump works fine on the bench test but there is no 12V coming back there. I short out the diagnostic terminal with the ignition turned to the on position and it will not run the pump. There is a relay (the one that I think is for the FP) located in the fuse box and it seems to be working.

Questions:

What should I do next?
Where is the FP Relay located (EXACTLY)?
Where is the EGI / PCM relay located (EXACTLY)? (wiring diagram shows the power coming from the FP relay and then on to the PCM EGI? relay and then on to the PCM.
Should I swap with a known good PCM?

Any ideas would be great. Also I have the identical car (running) sitting right beside it. This one as a tester if I need it.

Thanks for any and all responses. Please, for quicker response please also respond to [email protected]

Thanks again!

Mr. Tripp
Augusta, GA
 

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The fuel pump relay is in the main power box. That box has labels on the inside cover.
 

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Make sure you checked that all your spark plugs are secure, not full of oil from a Valve cover leak, and all plug wires are snug at both end.
 

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Discussion Starter · #5 ·
I don't have any fuel pressure....don't have any problem with oil in spark plug holes either. I can hear the FP relay click on and the fuel solenoid thing that attaches to the air box clicks as does the relay.

I do have somthing funny at the pump. The pump was taken off and when bench tested worked fine. I couldn't find power to the wires in the harness after disconnecting at all.

The book shows a black wire as the ground and the black with white stripe as the power wire in the harness. I looked at the pump itself and it has a red and a black wire coming off of it that stays inside the tank. Then if you follow the wires through the lid of the pump and onto the outside wiring...you can clearly see that the red wire from the pump goes to a black wire with light brownish/yellow dots on it, and the ground wire from the pump turns into a black wire with stripe. This is not as the book says it is susposed to be as the book shows the black with wire stripe to be the power wire??? go figure...

Bottom line, I can't get any power back there. Is there a separate fuel pump fuse separate from the relay(s)?

Thanks
Mr. Tripp
Augusta, GA
 

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I would trace the black wire with the brownish/yellow dots on it and find out where it does have power. Just find the next place where it connects to something else and see if at that point power was reaching it or not.
 

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I assume you heard the "click" sound (but no FP hum) when you short out the FP to GND in the diag connector. This is an indication that the PCM is doing it job in activating the FP relay.

Here is how you test out the FP circuit. You need a multimeter which gives you ohm (Rx1) and volt measurement.

1. unplug the FP relay (NF02)
2. measure the relay with an ohm meter. You will find there is a pair of connections (blades) on the relay reading about 100 ohm and the other pair of connections reads open circuit. Now the pair of connections that are open circuit are the contacts pair of the relay. Trace these 2 open circuit connections back to the socket of the relay in the fuse box. These would be the red/blk and wht/yel wires in the wiring diagram.
3. with key in OFF, use a voltmeter to measure the voltage of each connection from step 2, both should show zero volt
3. with key in ON(not START), use a voltmeter to measure the voltage of each connection from step 2, one should show 12V (red/blk) and the other one should show zero volt (wht/yel)
4. put key back to OFF, use an ohm meter to measure the wht/yel wire to a GOOD ground (negative pole of battery). It should read about 1 ohm

Chances are you will read a high resistance or open circuit from step 4 above. Since your FP is good so the culprit would be wiring / connectors.

First thing would be to find out were the FP is grounded. Since we have plastic fuel tank there should be a wire from the FP (blk) and get grounded on the chassis. This is the most likely cause IMO.

2nd would be the FP connector, make sure it is clean.

Otherwise it would be somewhere between the FP relay and the FP. Hope this helps and good luck.
 

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I am having problems getting my 93 2.5 running but I made these discoveries that might help you. There is a connector that feeds the fp behind the panel drivers side trunk. Also the connector under the car closest to the pump was soaked with water and showed signs of shorting.My wiring is the same as yours blk/white to black through connector???. A pos. and neg. wire both go through this plug. Before I discovered this short, my disti fried the components inside. Smoke pouring out with ignition on. A black/white wire feeds both the pump and disti so it's possible the fp wire caused the short in the disti. Also the ecu or icu may control both the fp and ignition although I haven't confirmed this to be my problem. I have fp issues as well although I seem to have good fuel pressure at the fuel rail(relays ok). Battery hooked up directly to the connector and the pump runs great. I have since done the HEI upgrade and have a spark but it may not be strong enough and I may have to replace the disti anyways.
 
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