10 Amp Engine fuse on an 89 FI

[dalebwilson]

In my opinion the 10amp engine circuit should not have continuity to ground. It could however be reading through other circuits, lights, coils etc. Has your wiring been modifed at all by the previous owner? Could you have any extra load put on the engine fuse? Try this temporarily to see if your engine will run.

Remove 10amp factory fuse and resinstall the relay. Install a 12V+ wire with inline 10amp fuse from the battery and temporarily splice to the black/white wire. Crank engine and determine if it will stay running. Remove temporary setup immediately when test is complete.

[gunnerw]

I just checked the blk/wht with the fuse out. No continuity.

[dalebwilson]

Remove the 10amp fuse and check blk/white to ground.


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[gunnerw]

Yes to both. new 10a fuse and blk/wht at connector to ground and blk wire to ground. both have continuity

[dalebwilson]

That's good. Your relay appears to be good. With a new 10amp fuse installed and the key off, check continuity on the black/white wire to ground. Then check the black wire to ground.


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[gunnerw]

I just checked each terminal to the metal case. None of them have continuity.

[dalebwilson]

Yes. That means the coil is good and the relay is functioning properly. Now check to see if you have continuity between any of the wires to the metal case of the relay.


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[gunnerw]

Dale I benched tested the relay as you suggested. The wires on the pig tail didn't match the colors that you listed but the wires in the connector that plugs to pig tail did. When i connected blk/wht to 12+ and blk to 12- the relay does click. When I checked continuity between the other two terminals, I only had continuity when the blk/wht and blk terminals are connected to the battery. Does that make sense

[dalebwilson]

You may need to try finding the relay at a Ford or Mazda parts counter. May be an OEM part that is not available through the chain stores.


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[gunnerw]

Movin: Yes the car will start and run for about 20 seconds the it blow the 10a fuse and dies and will not restart.

Dale: I am still looking at the wires to see if I have a grounded situation. I am having a hard time finding a replacement relay. I even searched by the part number on the relay (Denso 056700 8550) Autozone and O Rileys cant seem to find anything. Do you have any idea where to find this part?

[dalebwilson]

Is that what that is? a relay?

to what? I noticed that dangling near the battery, and some rust on my '91-

are you talking otherwise about a fuse in the main fuse box?

Does the circuit run through the fussy-ble links? maybe shorting there.

Yes....thats the main relay and it should be mounted on one of the bolts that the coolant resorvoir is attached to. Without the relay functioning, your car doesn't run. The 10amp engine fuse supplies power to the relay coil and the EGI fusible link supplies power to the relay contacts. With the ignition switch in the run or start position, the relay supplies power to the fuel delivery system. If the 10amp fuse continues to blow, the circuit is overloaded due to a bad relay or possible shorted/grounded wire.

[Movin]

Did you mean the car started , blew a fresh fuse and died, with the relay pulled out ?

[gunnerw]

The fuse I am talking about is a 10A fuse listed as "engine" inside the car on the fuse box. I replaced the fusable links with hard fues. I'll bench test it as suggested and see what i get

[harpon]

Is that what that is? a relay?

to what? I noticed that dangling near the battery, and some rust on my '91-

are you talking otherwise about a fuse in the main fuse box?

Does the circuit run through the fussy-ble links? maybe shorting there.

[dalebwilson]

Bench test the relay by applying 12V+ to the blk/white and 12V- to the black. Test continuity between white/blue and yellow/black.