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Discussion Starter #1
On a 90 5.8L where is the Fuel Pump Relay located? And, is the 12v for the radio presets run outside the dash or does it run to the fuse panel?

I did check my Ford shop manuals, and searched here. I have tried to backtrace the wire from the radio but lost it in the harness and thought it would be easier to simply look foolish :twak and ask then to start ripping the harness apart. :haha
 

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X2 on 12V Radio. As for the Fuel Pump Relay... it should be on the left side (driver's side) of the engine compartment toward the rear. It's a black box and the cover should indicate the relay locations... if not search around and it's probably posted somewhere on the forum. Or if you have it, check the Owner's Manual. It will actually diagram the exact fuse location of the 12v Radio and the Fuel Pump Relay. There is probably an inertia switch also... which shuts off the fuel pump upon impact (or fault). Not sure on the 90, but mine is behind the passenger side kick panel.
 

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Discussion Starter #4
X2 on 12V Radio. As for the Fuel Pump Relay... it should be on the left side (driver's side) of the engine compartment toward the rear. It's a black box and the cover should indicate the relay locations... if not search around and it's probably posted somewhere on the forum. Or if you have it, check the Owner's Manual. It will actually diagram the exact fuse location of the 12v Radio and the Fuel Pump Relay. There is probably an inertia switch also... which shuts off the fuel pump upon impact (or fault). Not sure on the 90, but mine is behind the passenger side kick panel.
Thanks with all my shop manuals and this site, I guess it's been 16 yrs or more since I even looked at the owners manual. I'll dig it out tomorrow.

I actually don't have a problem with the fuel system. I ran a cylinder test with my code scanner and it looks like I could have a injector problem or two. I was going to run a fuel pressure test and it called for relieving the pressure by unplugging the relay and start the truck to get all the pressure out of the line before I hook up to the shrader valve.

I guess I could have just unplugged the pump but I was frustrated because I couldn't find the relay. The radio intermittently drops the preset and there didn't seem to be any problem at the rear plug so I thought I'd run a continuity check back to the source but I couldn't find that either.

I guess I'll also be dropping the fuse panel tomorrow also.
 

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yo;

FP Relay Location in a 90; on driver's side fender apron

Source: by Seattle FSB (SeattleFSB) at SuperMotors.net

Location pic; EEC Power Relay (BROWN Connector) next to the FP Relay (GREEN Connector), Trailer Tow Relay (Grey Connector) & EEC Test Connector pic in a 90; on driver's side fender apron to the rear of the Airbox

Source: by Seattle FSB (SeattleFSB) at SuperMotors.net


Fuse Block Diagram in a 90 Source: by ElKabong (Ken, El Kabong) at FSB
 

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SnowTom... you will probably notice on the Fuse Block Diagram that miesk5 supplied, there are 3 fuses that wire to the radio; 8, 10, and 11. For radio presets you're needing the 12 volt constant... should be 8. I'm what I call an "over-chcecker". Might be worthwhile to (obviously) first check ALL fuses then take a multi-meter and make sure there is 12 volts at #8 when the ignition is off and the key is NOT in the ignition.

Being a 21 year old vehicle, there's no telling what's happened with the Radio wires, either.... especially if there was a previous owner... they could have rewired the constant to a different location... no telling. The wire could be loose behind your radio, shorting out against metal behind the dash, etc. After you've check the fuses and verified there is in fact 12 volts constant at the fuse box, start looking for 12 volt constant behind the radio. If the wire is there without 12v but you have it at the fuse block, test continuity between the wire and ground. If you start testing continuity directly to the fuse box, disconnect the negative battery lead first just to be safe. You can also jump a test wire from the #8 fuse directly to the 12v constant on the radio to verify it's not the radio malfunctioning.

But again... I'm an "over-checker" that has a problem with wanting to know why! lol. No constant behind the radio but good at the fuse box... new wire, done. I just tend to look deeper. Hope the info helps.
 

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Discussion Starter #7
SnowTom... you will probably notice on the Fuse Block Diagram that miesk5 supplied, there are 3 fuses that wire to the radio; 8, 10, and 11. For radio presets you're needing the 12 volt constant... should be 8. I'm what I call an "over-chcecker". Might be worthwhile to (obviously) first check ALL fuses then take a multi-meter and make sure there is 12 volts at #8 when the ignition is off and the key is NOT in the ignition.

Being a 21 year old vehicle, there's no telling what's happened with the Radio wires, either.... especially if there was a previous owner... they could have rewired the constant to a different location... no telling. The wire could be loose behind your radio, shorting out against metal behind the dash, etc. After you've check the fuses and verified there is in fact 12 volts constant at the fuse box, start looking for 12 volt constant behind the radio. If the wire is there without 12v but you have it at the fuse block, test continuity between the wire and ground. If you start testing continuity directly to the fuse box, disconnect the negative battery lead first just to be safe. You can also jump a test wire from the #8 fuse directly to the 12v constant on the radio to verify it's not the radio malfunctioning.

But again... I'm an "over-checker" that has a problem with wanting to know why! lol. No constant behind the radio but good at the fuse box... new wire, done. I just tend to look deeper. Hope the info helps.
Thanks to both you and miesk5, that exactly what I needed. My shop manual did show the radio on 11 but not on the other two. Do you think the Warning Buzzer on #8 is the Key left in the ignition buzzer?

The reason I ask is that I just replace the upper ignition actuator, and when I was done the turn signals wouldn't work. It turned out to be the Hazard switch, with is part of the turn signal assy. I have the new switch but haven't had time to install it yet. So, I'm wondering if something in the switch is drawing down the voltage enough for the radio to lose voltage on the presets.

It seems like too much of a coincidence to have two problems on the same fuse circuit.
 
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