Relay(s) on passenger side firewall

[LASVEGASLSC]

I am 'on the road' as we speak. Vehicle this morning let me down.....well.....for a few minutes. Turned off....went to restart moments later.......turned key....did not hear fuel pump run ...No start of course......did wiggle test everywhere...no change. Turned Key to Run position....wiggled everything eletrical under hood as well as fuel switch in trunk. I am told fuel pump relay is in trunk..left side..................But..............each time vehicle fails to fire.................I jiggle the the cover and the relay(S) under it on passenger side firewall............vehicle starts. If I shut off.......vehicle will not start...........wiggle pass side components again with key in Run position vehicle starts every time..............Which realys am I messing with there?

Thanks in advance
Dallas

[hypostang]

Electronic engine control relay ..... main relay for the cars computer

[Magic Al]

Relays in general:

http://thelincolnmarkviiclub.org/Gallery/albums/Relays/RelayLoc.sized.jpg

[gatlaga]

Relays on right passenger side firewall. Rear one is Fuel pump, front one is horn/Cruise control. (It is on my 91, don't ask how I know) The two are superceded to be the same, so you can swap'm if needed.

[LASVEGASLSC]

thanks for the good info.

[Magic Al]

Your fuel pump relay is in the trunk mounted to the LH hinge support. When the key is turned on the pump will run for about 2 seconds, then shut off if the engine is not started. This fuel pump relay gets it's power via the EEC relay.

That relay you are "shaking" is what Hypostang said in Post #2, the EEC power relay.

When the ignition is turned to Run or Start, power is supplied to this relays coil. When the contacts close, the EEC Power relay supplies power via fuse link "K" to the Fuel Pump relay. That's why you hear your fuel pump start when you move the wires.

This EEC relay also supplies power to the WOT A/C cut out relay, Fuel Injectors, ECA unit, EGR solonoid, Idle Speed Control sol, and Thermactor solonoids.

[Fordace]

Your fuel pump relay is in the trunk mounted to the LH hinge support. When the key is turned on the pump will run for about 2 seconds, then shut off if the engine is not started. This fuel pump relay gets it's power via the EEC relay.

That relay you are "shaking" is what Hypostang said in Post #2, the EEC power relay.

When the ignition is turned to Run or Start, power is supplied to this relays coil. When the contacts close, the EEC Power relay supplies power via fuse link "K" to the Fuel Pump relay. That's why you hear your fuel pump start when you move the wires.

This EEC relay also supplies power to the WOT A/C cut out relay, Fuel Injectors, ECA unit, EGR solonoid, Idle Speed Control sol, and Thermactor solonoids.

yeah, what he said, also, sometimes the rear glass leaks a little right on top of the fuel pump relay causing it to fail intermittently, but sounds like EEC power relay up front under hood....

[JSev22]

http://www.markvii-lsc.com/images/fuelpumppath.jpg

Blue = Voltage path with key to ON or START.
Red = Voltage path showing how fuel pump relay is energized.
Green = Voltage path showing how fuel pump is energized.

As stated, the relay you 'adjusted' was the EEC Power Relay. Not only does it apply voltage to the fuel pump relay but many other sensors/controls as well.

[demonswede]

Does this rear fuel relay work like my CrossFire camaro's - when defective

Car starts cold - when hot no start until cools down and & oil gets thicker.

Reason - low fuel pressure cut out fuel pump (front relay?), will not BY the STARTER MOTOR give oil pressure enough to start pump without the rear (talking lincoln here)

But Will WHEN Cold Engine.

Had very hard to find the obstacle - wife said start start (when warm & shopping) but I realized that it would only make us sitting due to dead battery.

[Tony T]

Does this rear fuel relay work like my CrossFire camaro's - when defective

Car starts cold - when hot no start until cools down and & oil gets thicker.

Reason - low fuel pressure cut out fuel pump (front relay?), will not BY the STARTER MOTOR give oil pressure enough to start pump without the rear (talking lincoln here)

But Will WHEN Cold Engine.

Had very hard to find the obstacle - wife said start start (when warm & shopping) but I realized that it would only make us sitting due to dead battery.

No, lincoln(ford) does not use oil pressure to activate pump. Al has it right, the fuel relay coil is powered by the energized EEC, the ground side is controlled by the EEC in start or when EEC detects a minimum RPM. Sounds like your chevy either needs oil pressure switch or (shudder) has no oil pressure.

[demonswede]

On the camaro/gm if you have an accident & engine stalls & ignition on - there is no oil pressure & pump stops running - thus if accident & fuel line cuts off pump shall not run for avoiding fires.

Therefore the the short sequence fuel pump relay is necessary for fast starting or starting in hot (with low oil pressure by starter motor).

Are there no oil pressure fuel pump cut out on Fords??

[JSev22]

On the camaro/gm if you have an accident & engine stalls & ignition on - there is no oil pressure & pump stops running - thus if accident & fuel line cuts off pump shall not run for avoiding fires.

Therefore the the short sequence fuel pump relay is necessary for fast starting or starting in hot (with low oil pressure by starter motor).

Are there no oil pressure fuel pump cut out on Fords??


Ford uses an inertia switch in the trunk to shut down the fuel pump in collisions, you can see how it's used in the drawing I posted.

[Tony T]

Ford uses an inertia switch in the trunk to shut down the fuel pump in collisions, you can see how it's used in the drawing I posted.

What he said plus if engine stalls EEC detects this and shuts off fuel pump relay ground.