1989 bronco wont run

I have a 1989 bronco with automatic and the 5.0 in it. I fried out a eec relay and fuel pump relay and replaced it still no power to the fuel pump unless i use a jumper 3 relays and they were all brand new and tested ok. But even with a jumper the pump runs and get fuel to the rail but only runs for a second maybe two. Any ideas here? EEC? Map Sensor? Bad ground? I am so lost on this one

when I got my 89 I had the same problem. No power from the eec to the fuel pump relay. I think I found that it was the yellow wire? So I ran a wire from the battery to the yellow wire at the relay and I ran I like that for 3 years. I assumed the eec had been fried and never bothered to fix it.

I believe that the EEC relay triggers the fuel pump relay.

It then supplies power THROUGH the inertia switch to the pump.

WIth a test light check for power at both sides of the inertia switch.

If no power at either side of the switch, then you have a relay problem, or fuse problem to the relays. There may be two fuses, one for each relay, I am not sure.

How to check a fuel pump relay

http://broncozone.com/forums/index.php?showtopic=14905

The engine will not start. There is no spark and no communication with the Powertrain Control Module (PCM).

Tests/Procedures: 1. Check for spark and fuel pressure.

2. If no spark is present, pull the spout connector and retest for spark. If spark is now present, suspect problems with the Electronic Engine Control (EEC) power relay.

3. Check for battery voltage on the solid Red wire that goes to the Idle Air Control Valve (IAC). This is the same wire that powers up the Powertrain Control Module (PCM) at pins 37 and 57 from the EEC power relay and feeds power to the primary side of the fuel pump relay. If there is no voltage, check the Yellow wire that feeds the relay. This should be hot at all times and comes from fuse link N at the starter relay.

4. If battery voltage is present, check for the 5-volt reference voltage that is the output from the PCM at the Orange/White (O/W) wire at the Throttle Position Sensor (TPS).

5. If no reference voltage is present, suspect a shorted 3 wire sensor or a shorted O/W wire to ground. Unplug all of the 3 wire sensors one at a time to see if the reference voltage returns.

6. If the reference voltage does not return, cut the wire at pin 26 of the PCM leaving enough wire to solder the wire after diagnosis. Check for 5 volts on the PCM side of the wire.

7. If 5 volts is now present, there is a short to ground on the O/W wire between the PCM and the engine compartment.

8. If there is no 5 volt reference after cutting the wire, and there is battery voltage on the Red wire at pins 37 and 57, the PCM will need to be replaced.

o power like the old one so I'm off to junk yard I think to see if I can find the right parts cause the dealer keeps telling me they don't have my four prong relay all they have is a five prong which doesn't work either.. neither relay is giving power out the other side. Fuses all were good as well as all the fusible links I found. Any more Ideas I'm up for them and thanks for all the input guys. I have worked on cars since I was 15 and always hated wiring lol so I stayed away but I like this bronco and it will run again...

I am now getting power thru the relays but the pump isnt kicking on. The pump will run with a jumper wire inserted where the relay is but only starts for a second then shuts off still. And still no power to the inertia switch at all.

I am now getting power thru the relays but the pump isnt kicking on. The pump will run with a jumper wire inserted where the relay is but only starts for a second then shuts off still. And still no power to the inertia switch at all.

This can not be true.

If the pump will run when you jumper out the relay, then you MUST have power to both sides of the inertia switch.

Therefore you must not be getting power through the relays.

I posted a link on how to test a relay, if you don't understand it, then do yourself a favor and go buy a new one. About $20

BroncoJoe19 said:

I am now getting power thru the relays but the pump isnt kicking on. The pump will run with a jumper wire inserted where the relay is but only starts for a second then shuts off still. And still no power to the inertia switch at all.
This can not be true.

If the pump will run when you jumper out the relay, then you MUST have power to both sides of the inertia switch.

Therefore you must not be getting power through the relays.

I posted a link on how to test a relay, if you don't understand it, then do yourself a favor and go buy a new one. About $20

Click to expand...

Understood very well and have bought 3. Thats what is getting me unless its jumped there is no power to the fuel pump or inertia switch. It makes not one bit of sense. Its honestly driving me nuts the only thing i can think of is the computer but even that is not making sense

ok I just talked to my stepdad and he said we are now getting power to the inertia switch but it wont run off the relay just when jumped or tested from the dlc

Did you try swapping out the EEC relay?

Did you check the fuse to it?

Do you have power to the fuse?

Did you check for power to the EEC relay, and did you check to see if you get power to the trigger side of the EEC relay when you turn the key to ON/RUN?

BroncoJoe19 said:

Did you try swapping out the EEC relay?Did you check the fuse to it?

Do you have power to the fuse?

Did you check for power to the EEC relay, and did you check to see if you get power to the trigger side of the EEC relay when you turn the key to ON/RUN?

Click to expand...

1) eec relay is swapped yes

2) cant find a fuse for the eec

3) eec relay has power to and from it

thanks Joe Im really trying to get this running and not waste alot of money your tips are much appreciated

Each relay gets power to it from two different locations.

A relay gets power to it from somewhere (the battery by way of a fuseable link, or from a fuse box), it relays this power to somewhere else, typically a heavier draw item like a pump or fan.

The relay also gets power from whatever triggers it to relay the power mentioned above.

The EEC relay should have two sources of power.

1. from the battery (fuesable link)

2. the trigger from the ignition switch when it is turned ON/RUN, or STart.

Question... does it have power from both sources?

IF the answer is YES,

THEN check the fuel pump relay for two sources of power.

(note: the Fuel pump relay gets triggered from the EEC relay, so the EEC relay has to be in its socket and the key turned to on/run to test for the trigger source of power to the fuel pump relay.

BroncoJoe19 said:

Each relay gets power to it from two different locations.A relay gets power to it from somewhere (the battery by way of a fuseable link, or from a fuse box), it relays this power to somewhere else, typically a heavier draw item like a pump or fan.

The relay also gets power from whatever triggers it to relay the power mentioned above.

The EEC relay should have two sources of power.

1. from the battery (fuesable link)

2. the trigger from the ignition switch when it is turned ON/RUN, or STart.

Question... does it have power from both sources?

IF the answer is YES,

THEN check the fuel pump relay for two sources of power.

(note: the Fuel pump relay gets triggered from the EEC relay, so the EEC relay has to be in its socket and the key turned to on/run to test for the trigger source of power to the fuel pump relay.

Click to expand...

Now here is where I may have a problem the dealer gave me a 5 prong relay said the 4 prong was discontinued but this would work in its place. anyone know if this is true??

It'll probably work. In fact your old one may still be good.

Get yourself a test light. I bought mine for a dollar at a dollar store. Actually at that price I bought two!

Then test for power where I mentioned above.

All you have to do is ground the lead, and then with the probe test each of the four contacts of where the relay plugs in. One of the big holes should have battery power, and one of the little holes should have power with the key turned ON.

Then for the fuel pump relay you must have the EEC relay in place, and do the same test.

Let me know what your results are.

If you don't understand, ask your grandpa to read this.

ok the eec shows power from 3 wires(2 of which go into one socket which is constant) with the key on

the fpr shows power from 2 wires with key on..

Now if The FPR has 2 power sources shouldnt there be 3 wires showing power with the key on??

what the heck is n3?

BroncoJoe19 said:

what the heck is n3?

Click to expand...

lol me trying to type to fast supposed to be 3

no for the fp relay there will be two big pins and two little pins.

One little pin will get power from the EEC relay, the other little pin will go to ground, (I am guessing that ground is controlled by the PCM)

When the one little one gets power from the EEC relay, and the ground is grounded, that will trigger the fuel pressure relay to make the connection accross the two large connections. This will permit the power to get to the fuel pump.

Can you back probe the connector that the fuel pump relay plugs into? If so, then back probe the large pins with your test light, and ground the test light lead. One large pin will always be hot, the other pin should also be hot when the relay is triggered. So have someone turn the key off, and then back on while you are backprobing the conenction, it will only stay triggered for a couple of seconds after you turn the key to ON.

IF you get power there, the relay is good, and it is being triggered. You already know that the wiring from the inertia safety switch is good (because you can get the pump to run by way of the DLC) so you will now need to test the wire from the big connector from the fuel pump relay to the inertia switch.

IF you do not get power there, then the relay is bad, or it is not being triggered. You already tested the trigger side and you know that it is getting power, so it must be a problem on the grounding side. So we'll have to check the grounds to the PCM. I think that it is the one that is nearby the PCM, near the firewall on the driver's side.

I redid the ground on the firewall because it looked bad today( previous owner actually spliced it in 3 times and one was a bare wire about 8 inches long) it fired up and died as usual. And i switched the relay again what would cause it to not be triggered??