Here's my problem, I have an 88 ford F450 (Flatbed) 7.5ltr Manual tranny EEC IV. It was running fine until one morning it refused to start. Engine is cranking fine. Its getting spark because when I spray starting fluid into the throttle body it fires up for a few seconds then dies. I found that the fuel pump and injectors are not activating. So far I have changed the fuel pump in the tank, changed the fuel pump relay, the eec relay, the distributor module and the EEC IV computer. When I ground the neg test wire at the plugin connector I get pressure on the fuel rail 40psi. I tried starting it with fuel pumps jumped and still no start, so its not the fuel pumps (I have single tank with inline and intank pumps) I have tried retrieving codes but am not getting a reading from old EEC or new EEC. Where do I go from here. I gotta get my truck up and running HELP!

 

Sounds like you are not getting the "PIP" pulse to the EEC Module (Computer) pin 56 over the DK BLUE wire #349 from the TFI Module.
Or you are not getting power to pins #1, 37 & 57 of the EEC Module (Computer).

Here is a Diagram.

http://www.autozone.com/images/cds/gif/large/0900823d800a3a44.gif

 

Thank You for the info and diagram Subford ......... I'll be working on the truck on Monday at work, I'll follow your advice and see what happens. I will get back to you Monday evening and let you know the results. I really apreciate the response...... Thank You.

 

Possibly a blown fusable link... you might want to have one handy if you happen to be in the neighborhood of your parts store.

Let us know how you make out.
Tim

 

Also if you have a small black wire coming off the NEG (-) post of your battery (that looks like it has an inline fuse holder in it about four inches from the battery), make sure this wire has a good connection to the battery and the plug is together. It is the EEC Computer ground. Make sure you have a good body ground also.

 

Thanks again Subford, I will check that ground wire and inline fuse as well ....... What pin no on the EEC does the battery ground go to?
Thanks Popa Tim ...... so far I've checked all fusible links that I can visibly find but I'll double check those as well.

 

It looks like inline fuse holder, it is not a fuse, it’s a plug. It should be a Black with a Light Green stripe wire and goes to pins 40 & 60 of the EEC.
Check that body ground also.

 

OK Subford you've earned my respect....... but im not out of the woods as yet. You would not believe what I discovered...... That black ground wire that goes to the negative post on the battery? Well it was attached to the positive post of the battery
....... Talk about MAJOR F*** UPS , LOL......... anyway I reconnected it to the negative post and still no start. But now im getting 2 fault codes from the EEC.... 87 and 96 which both point to the fuel pump relay, which I just changed when this happened. Now here is the catch, when I jumped the ground wire on the data output connector before I got pressure on the fuel rail even with the key in off position but no start (no injector power up) ...... Now with the corrected negative wire in place I still get no fuel pump cut on ........ but when I jump the data cable ground I get fuel pump power up with key on only ...... And the truck FINALLY STARTED (Thank you Jeezus)
So now im getting close I need to get power to my fuel pump from the EEC and I'll be home free ........... Stay with me Subford you've been a major help so far .......... WHAT NEXT !!

 

OK those code say that when the EEC sinks the Tan wire with a Green stripe to ground from the Fuel Pump Relay it is not getting 12 Volts back on pin 8 of the EEC from the Brown wire.
When you say, "but when I jump the data cable ground I get fuel pump power up with key on only", are you saying that you are jumping from Pin #6 on the TEST CONN to ground?

OR are you saying you are jumping the Yellow wire at the Fuel Pump Relay to the Brown wire?

 

Here is a diagram of the Test Connector (DLC).
You ground Pin 6 to test the fuel pumps and fuel pressure, the pumps will run as long as pin 6 is grounded. Pin #2 (BLK/WHT wire to pin #46 of EEC) is ground and goes back over the Black green wire (by way of pin 40 & 60 of the EEC) to the Neg(-) post of the battery.

 

What I meant was when I ground pin #6 (grounding it on the chassis) of the data link connector I get power to the fuel pumps with key on.(with key off there is no power to pumps even with #6 pin grounded) She then can start up. So injectors are now working. I now need to resolve the fuel pump connection problem and I'll be back on the road. Also is there a difference between the fuel pump and EEC relays or do they both do the same thing? .... I might have mixed those relays up, the replacement relays are both all black.

 

If the pumps come on with pin #6 grounded than the relay is OK, that is all that the EEC does when it turns it them on.

You might try jumping pin #2 to pin #6 of the data link connector to make sure the ground is OK and they run, but this is a long shot.

If they do and not with the EEC then either you have a bad wire (Tan/LT GRN) from the fuel pump relay to the EEC pin #22 or the plug is not making good contact at the EEC.

If this is all good than I would say you have a bad EEC, more than likely from the ground wire on the POS post of the Battery.

 

Thank you again Subford ....... I did a lot of testing today, I found that no ground signal is being sent from the EEC to the relay. (tan & lt green wire) When I tested that wire with key off I got a dim light with my test light, that is connecting my test-light jumper to the positive side of the battery and prodding the wire with the sharp point of the test light ....... with key on the dim light goes totally out ( no ground whatsoever) I think you may be on target with the damaged EEC, but both EEC's 0ld and new one must have been damaged in similar way. Anyway what I did today was leave grounded jumper wire in pin #6 of data connector and the truck drove beautifully. When the key is off the relay is also off ...... The only problem is once the key is in the on position the fuel pump stays energised even if the engine has not been started as yet .... I realise that this overrides a safety feature of the vehicle but do you see any serious danger in doing this or do you think I can get by with this for the time being??

 

No serious danger in doing this, other than the safety problem and you all ready know that.

 

The bottom line is my truck is up and running..... Until I can find a used EEC to test, Im going to leave it as it is..... I really just want to say something before this thread is ended...... I mostly frequent the Diesel Forum on this site as my main transportation is my 95 PSD ..... It is the first Diesel truck that I ever owned, I never worked on a diesel engine before I bought this truck but up until now I have never had to go to a mechanic for repairs........ Every problem that I have had with this truck I have found the answers on this website ........ If not for this site I would have paid out major $$$ by now in repair cost .........(By the way Im not a mechanic, Im a factory manager) My 88 F450 is used at my workplace as a delivery truck and without the help of this site I would certainly have had to pay out a lot of cash to have it repaired. It is most important to me that I get the message out to the experts on this site as to just how very appreciative I am of their help. Guys like Subford who seemingly check all new post to see if they can be of assistance to those requesting help and knowing that there is no payment in return...... It is uplifting to know that people like him still live on this planet...... The vast majority of people on planet earth will do NOTHING for you if there is no return to be gotten. I for one am thankful for these good people ...... More of us should be thankfull !! .......... Thank You Subford Your help is very appreciated.