Fuel Having issues getting my fuel pump to work.

evintho

10 Year Member
Nov 12, 2003
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Santa Rosa, CA.
When turning the key to 'ON' the fuel pump should run for a couple of seconds, then shut off....correct?
That doesn't happen. The only way to make it work is to jump power to pin #87 (Bosch style relay) and it'll run constantly. Doesn't build up fuel pressure 'cause there's no fuel in the tank. Just trying to get everything working before I fire it up for the first time.

Some context:
'93 5.0/AOD and wiring harness swapped into my '54 Customline. New Walbro pump installed in the '54 tank. Running factory fuel injection with ECU and all the factory wiring. No inertia switch. I'm using the large factory wiring diagrams for reference.
Wiring is:
#787 PK/BK from pin 30 to starter solenoid on inner fender.
#238 GRN/YEL from pin 87 to ECU and also to fuel pump.
#361 RD from pin 85 to ECU.
#926 BLU/ORG from pin 86 to ECU and also to data link connector.

With key 'ON', there's no power to #787 which makes sense 'cause the start solenoid contacts haven't closed to transfer power from one side to the other. However, when the key is ON shouldn't the ECU provide power to the relay to cycle the fuel pump? I can hear the ECU relay click on.
I've been fooling with this for days and have kinda hit a wall!
 
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evintho

10 Year Member
Nov 12, 2003
525
127
73
66
Santa Rosa, CA.
Dumb question. Is this what's meant by 'jumpering EEC test connector to ground'? Just running a wire from the lower right terminal to a ground stud?

P1010002_8 (2).JPG
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Well, not exactly.
There is a wire that gets connected when doing the code check, look for it in the harness near the test connector.
 

evintho

10 Year Member
Nov 12, 2003
525
127
73
66
Santa Rosa, CA.
Thanks for responding General! Actually, I'm not dumping codes, I'm trying to troubleshoot why my fuel pump isn't priming. I'm following JRichker's 'fuel pump troubleshooting for '91-'93 Mustangs'.

Relay: Turn on the key and jumper the ECC test connector as previously described. Look for 12 volts at the dark green\yellow wire (relay controlled power for the fuel pump). No voltage there means that the relay has failed, or there is a broken wire in the relay control circuit.

So, my pic isn't correct?
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
24,030
8,890
203
polk county florida
This will give you wiring diagrams and tell you how to jump the fuel pump.
 

evintho

10 Year Member
Nov 12, 2003
525
127
73
66
Santa Rosa, CA.
OK, is this how to jump the fuel pump? Red wire from upper right terminal to Pin 46 terminal?
The harness isn't in a Mustang but I've swapped a '93 motor/trans/ECU and wiring harness into my '54.



1669934268013.gif
 

evintho

10 Year Member
Nov 12, 2003
525
127
73
66
Santa Rosa, CA.
Yeah, I just jumped it and no joy.
I can run power directly to #87 on the relay and the pump works.
I have a Bosch style 5 pin relay and with the key ON I've got 12v to every terminal except #87. There's even 12v to #86 which is the lt blu/org wire that runs to the ECU/data connector. That's on the other side of the relay coil...shouldn't that be 0 volts? Maybe not.
I've swapped relays also with same results.
I think all that's left would be a broken lt blu/org wire that runs from the ECU to the relay. I'll have to check that.
 

evintho

10 Year Member
Nov 12, 2003
525
127
73
66
Santa Rosa, CA.
OK....I cut the lt blu/org wire 6" out of the ECU and ran a jumper wire from there directly to #86 on the relay and the fuel pump primes! The wire must be broken somewhere inside the harness. Now I have to replace it but at least I found the problem! Thanks General!
 

manicmechanic007

5 Year Member
Sep 26, 2017
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Like to see a pic of your 54
I will compare my diagrams to yours if you need
It's the processor that grounds that fuel pump relay for a few seconds
You need to be looking at the ground signal into the green FP relay from the processor imo