Any REAL experts on here?

Cass opined in "Any REAL experts on here?"

Sorry, I've never had the pleasure of owning a MkVIII..

So I wouldnt have the slightest idea.

Thanks, Backyard.

I am not so sure that it is a pleasure. I will make that decision when I get it running.

I have the service manual and the electrical manual but not the power-train manual.

One would think it wouldn't take a huge effort to determine the problem in why the fuel-pump relay is not being energized but it does.

I don't know of any groups to go to other than this one and rec.autos.tech.

Cass

Cass, You may want to share the year with us, this could have EEC4 or 5. Either way, the relay has power supplied by the battery all the time. The variable is that ground for the relay is provided by the PCM, which sends power to the fuel pump. Your EVTM should be enough to troubleshoot this. Make sure that power comes in where it should, if that's OK, try grounding the wire to the PCM instead of holding the relay, if this works, trace your wiring or check your PCM.

i got a 93 taurus and the integrated control module(constant control relay) did the same thing to the a/c (voltage to the a/c compressor).. probably got what i have... i got the $65 shop manual and the $32 electrical/vacuum trouble shooting guide, but i like you dont have the Power control manual which helm want $300 for... the books i have walk you to the steps to check everything up until the Power control.. that is where mine stopped also... i got the a/c working dont know how, it just started working.. i think it was the contacts in the relay for the a/c i did not take the module apart to find out yet.. next time it stops working i will.. i have been on various newsgroups/boards with this and found that some people check the relay by taking it apart and resoldering wires in it.. probably not your problem as you get no signal from the Power control module to the relay.. on mine if this is the case there is another relay(sensor??) that is not operating correctly and feeding bad info into the Power control module...look for that in the electrical/vacuum troubleshooting book....

Cass opined in news:bjgv7n$bl5$ snipped-for-privacy@pita.alt.net:

Well... try this shot in the dark from a non-expert.

With key on, check for 12v on the red wire/Lt Grn stripe

- This should be there, since the engine runs when you hold relay closed.. this power also sets the PCM relay

then check for grd on Brown wire/white stripe,

this Gnd comes from the "VCRM" Which is digitally (not individual signal) controlled by the PCM.. meaning dead end.

Hope it's the relay

Note the Pink/Blk from the PCM is a "sense" wire, not used for control. It may confuse you if you open the inertia sw as it has a lo-current voltage

If you ran codes, it should tell you about the failure.. which you already know

Backyard Mechanic opined in news:Xns93F064722C64BkMch6d@216.168.3.44:

AS key is turned on! Or with relay held closed, engine running

Backyard,

It isn't the relay as I put 12 volts on it and it pulled in just fine. The high side of the relay coil is getting 12 volts when the ignition is turned on. What is ISN'T getting is the ground that should be applied to the other side of the relay.

I don't know what wires you are talking about when you are calling out their color.

The inertia switch has nothing to do with this problem as when I push in the relay, the pump runs. If the inertia switch was open, the car wouldn't run.

What you are saying about the VLCM makes sense as it seems that the data buss from the PTCM is sending data to the VLCM and telling it what to do about the pump.

No code is showing on the computer that I built for this task. I didn't write the software so I am not sure that it even addresses this problem.

Thanks

Cass

Pygocelis,

I'm sorry, I thought that I had mentioned the year but see that I did not.

The car is a 1996 Lincoln Mark VIII.

As I mentioned in another post, the relay IS getting 12 volts and if I ground the other side of the coil, the relay pulls in. The problem is that the relay is not being grounded and that ground comes from the VLCM and that unit is told what to do about the fuel pump by the PTCM. So, I am not sure if the problem is IN the VLCM or the PTCM or perhaps both.

Thanks

Cass

Jim,

Thanks for the reply.

The a/c clutch is controlled by the variable load control module in mine, as well. My module also controls the engine cooling fan. The fuel pump gets turned on by this module but the module gets info from the power-train control module and as you say, I suspect some sort of other sensor is telling all of this to NOT turn on the fuel pump.

I will keep plugging.

Cass

ihave the ford CD for 1996 and will look into the cd tonight and see if i can find anything for you... it has the ford/mercry products in it... dont know about the MarkVIII, but will give it a try..

Thanks, Jim. I would appreciate it.

I just bought a 17 cd set about Ford. It hasn't arrived. The guy says that it is the same information that Ford uses. I don't know if that means the cds are from Ford or it has Ford info contained on the cds.

This has been a real beast to diagnose.

Cass

Cass opined in news:bjien6$4r4$ snipped-for-privacy@pita.alt.net:

Are you able to pull the stored or continuous codes with that? It SHOULD show that FUEL PUMP Primary or Secondary is failing.

The wires (colors) are the ones shown in the 93-94 EVTM.

Thus it seems the fault is in the VLCM/VCRM - whatever.

I DONT know if you can just replace that unit or if it has to be Initialized with the PCM, as in case of instrument cluster.

If one wanted to be creative, one could design a simple logic board using a few chips that would emulate the EEC IV setup with PCM power transition and injector pulses as inputs and supplying a 2 second hold-over grd thru pwr transistor to the low side of the relay.

Backyard,

The earlier Variable Load Control Units had relays inside so they were called VLCR. This and later modules have mosfets in place of the relays hence the VLCM.

I understand the colors that you were referring to after you said the EVTM.

Yes, I had thought of putting a 'one-shot' designed for a two-second pulse to pull in the relay but I would prefer to get this working on its own. I can just imagine the consternation it would cause if this vehicle even went in to a dealership for service. It the tires were out of balance, they would claim the one-shot was responsible.

There are no codes showing fuel-pump failure on this computer diagnostic board that I built. I will check it again just in case.

I hope that you are able to see something on your cd that gives an indication of how to find out why this fuel pump relay is not getting ground.

Thanks

Cass

Pygoscelis,

Thanks for the diagram. I have that one. However, I have traced the wires associated with the VLCM to the fuel-pump relay and all are good and measure < 1 ohm. I also am getting 12 volts to the high side of the relay. I have measured the feedback circuits from the VLCM back to the Power-train control module and all look good. I have measured the grounded side of the f.p. relay back to the VLCM and it is good so, it has to be that either the VLCM is not being told to turn on the relay or the VLCM itself is defective OR the PTCM is not telling the VLCM to turn on the f.p. due to some other sensor give the PTCM the information to hold off on the fuel-pump power.

The pins on the VLCM are fine as are the pins inside the connector that mates with the VLCM.

I just wish I knew how to tell which module it is. It has to either be the VLCM or the PTCM UNLESS it is a sensor going to the PTCM telling it to not power the fuel-pump.

This one is a real Sherlock Holmes job and is a challenge to me.

Thanks for the document.

Cass

Cass opined in news:bjjfi9$8u9$ snipped-for-privacy@pita.alt.net:

From what I see and what you say about the thing running okay if you ground that side of the relay... it's a 99.5% pure certainty that you got a blown Mosfet. ESP if you can get the fans to run and not run.

Like I say, I'm using the 94 edition.

Jim,

Thanks for the document. It is a little hard to read as it is squashed down. Also, it seems to be just a sort of block diagram or theory of operation in block form rather than the actual circuitry. Where your document shows a pin 13, for control of the relay, my book shows pin 12 of the VLCM going to pin 80 of the PTCM.

IF IT IS REALLY PIN 13 then, that may be the problem as that hasn't been checked, that I can recall. Pin 13 isn't even called out in the EVTM other than showing it in the pictorial view of the EVTM.

Pin 30 is the high side of the relay contacts while pin 87 is going to the fuel-pump; both of these being on the VLCM. Your document shows different pins.

What a beast!

Thanks

Cass

message

Backyard,

That is a great guess and is what I originally thought, too. However, after checking the mosfet associated with the fuel-pump relay, it shows good and even compares with the junction ratios of the other identical mosfets.

So, that leaves the remaining possibility that the gate of the mosfet is not being turned on in order to switch the 12 volts from its source to the drain, assuming a PMOS device.

Okay on your manual being a '94.

I am looking forward to running the computer diagnostic again and seeing if magic has changed anything.

Thanks again for your input.

Cass

Cass, the pcm grounds the relay for three seconds with key on. This primes the fuel line before starting. After the pcm receives a pip (rpm) signal it grounds the fuel pump relay when neccesary. Hook up a test light with the ground clip on the positive batt terminal and the probe in the processor ground terminal of the relay (sorry, i don't have a schematic in front of me) and turn the key on. You should see light for three seconds. If you don't see a light for three seconds the processor is not grounding the relay. Remove the 60 pin connector from the processor and ohm the wire between the processor connector and the fuel pump relay. You should have less than 5 ohms. If you do the wire is good. At this point you have to look at the processor as the probable cause. If the vehicle runs as you stated chances are that everything else in the system is ok and the cause is the processor however 75% of processor replacement is needless. keep that in mind. If you have any questions please post them and I will locate a electrical manual for more precise info.

John

PC PODD opined in news:- snipped-for-privacy@comcast.com:

He's way past that level.

My 94 EVTM for the car shows it's controlled from the DLC. The relay driver isnt working and problem is in logic for the drive transistor.

Ford keeps changing the names of the thing but it's like a separate "driver/controller" for relays - also controls fans.

You're right in regards to previous configurations, though.