Car won't start, actual diagnosing has been performed.

[94m5]

Hey guys,


I have been out in the shop all friggin day trying to get the 94 started for my dad. When this all started we figured it was the fuel pump as it has almost 200K on it. after swapping out for a new unit, I went to try and start but the same bull went on.


Next, I moved on to the custom PCM harness that I had to fabricate for the 5-speed intall, that is all tight, and right. I am getting momentary ground at pin 22 on the ecm when I 1st turn the ignition (to prime the fuel system for start up), but nothing else. If I take the fuel pump relay out from the underhood box, and jumper the terminals I can get the pump to activate on high speed only, and the car will start just fine.

After looking through my 93' electronics manual, I noticed that the pump is ran by the VLCM, to facilitale low, and high speed modes. How many people have had a problem related to the fuel side of this module, and COULD this cause a no start problem? And if not, What have been some common issues with this?


Thanks guys.


Mike

 

[driller]

I don't have my service manual or EVTM here but I would check/replace both the fuel pump relay and the battery feed maxi-fuse for the same circuit. IIRC, the battery feed circuit to the VCRM is hot all the time. Also the circuit actually uses 2 pins at the VCRM for current carrying capacity.

Verify fuel presence or absence with fuel pressure guage on the fuel rail.

Do a 'wiggle test' of the cam and crank sensor connectors as well as you may be chasing a ghost.

 

[02LSE96LSC91SE84TC]

Something go wrong with the inertia switch.

Your tests may have ruled it out, just quessing.

 

[94m5]

Would'nt be the inertia switch because I can jump the contacts under the hood and make it run. I have power on both sides of the maxi fuse with the ignition on, which means it is good. I also swapped the relays position for position and still nothing.


Thats why it points me to this module.


any ideas?

 

[driller]

As much of a PITA it may seem, the best method to test a VCRM is to swap it out with a known good unit(say from the '95?). If it still fails to run, an open circuit is most likely.

From what I understand of the VCRM, the fuel pump output is normally a pulse-width modulated voltage. You can test pin 24, circuit 787(PK/BK) for voltage. Also that circuit will have 12VDC when the high speed fuel pump relay is energized.

 

[94m5]

So, your saying pin 24 should have 12V+? with the ignition on, or when the high speed relay kicks in?


I would also like to know, WHERE does this relay get it's ground signal? is it from the pcm, or the VLCM?

 

[driller]

Pin 24 will have a modulated voltage signal until the high speed pump relay is energized. With the high speed pump relay energized, pin 24 is essentially back-fed +12 VDC.

The high speed fuel pump relay is grounded via the VCRM pin 10.

You may be onto something as far as the ground. Check circuits on pins 1, 8, 16 and 22 for continuity to ground. Of course also check ground G101 on the LH front of engine compartment(just under plastic cover with headlight access doors) as well as G104 on the RH front of the engine compartment.

If you have the EVTM, see sections 33-1 and 33-2 for a better mental picture of the VCRM circuitry.

 

[94m5]

Thanks driller, I have the same diagrams in the 93 manual, but its not here right now.


Thanks alot for your help.

 

[Moes8]

does this mean anything to you?dont know if it helps,but cant hurt to offer it.



Fuel Pump Circuit Operation

When the ignition is switched to the ON position, it turns the EEC Power Relay on. The EEC Power Relay provides power to the EEC-IV processor and the control side of the fuel pump relay. Power for the fuel pump is supplied through a fuse link or high current fuse attached to the starter solenoid (battery side). From the fuse link or high current fuse, current flow is through the fuel pump relay and Inertia Fuel Shutoff (IFS) switch to the fuel pump. The IFS switch is a safety device used to shut off the fuel pump in the event of a collision. If the IFS switch is "tripped," it must be reset by depressing the white or red button on the top of the switch. The fuel pump relay is controlled by the Powertrain Control Module (PCM).

When the ignition switch is turned to the ON position, the fuel pump will operate. If the ignition switch is not turned to the START position, the PCM will shut the fuel pump off after approximately one second. The PCM will operate the fuel pump when the ignition is in the START position to provide fuel while cranking.

After the engine starts, the PCM will continue to operate the fuel pump unless the engine stops, engine speed drops below 120 rpm, or the IFS switch is "tripped."


Fuel System Description for Taurus Flex Fuel and 4.6L-4V Mark VIII

The Mark VIII has a DUAL FUEL PUMP VOLTAGE system ( «Figure 11» and «Figure 12») to aid in fuel system noise concerns. The fuel pump operates in the high voltage mode (12-14 volts) during crank (for 5 to 60 seconds depending upon engine temperature), after start-up, at engine speeds in excess of 3300 rpm, and during periods of Wide Open Throttle when maximum fuel delivery may be required. The normal operating mode calls for low voltage (7-10 volts) to the fuel pump. This minimizes operating noise. Fuel pump operation is controlled by the PCM. The fuel pump operates in the same manner as all other systems except for the two speed feature.




NOTE:
Maximum fuel pressure is obtainable at WOT or the vacuum hose removed from the fuel pressure regulator.

If fuel lines/systems have been drained or evacuated, it may take up to 15 seconds to obtain the pressure specified.


System Diagnosis

NOTE:
Grounding the FP lead at the DLC will allow the pump to run continuously with the ignition switch on. For specifics of this DLC connector, refer to the Electrical and Vacuum Troubleshooting Manual.

 

[vr4]

now i dont know if ckt 926 is supposed to always have ground or not but im looking at a bad VCRM.


reading the note in the previous post would isolate it to either the VCRM or the PCM depending on results

 

[Psychostang]

Have you made any progress. My 96 has been hot wired since I bought it. Previous owner brought it to a shop, and they couldnt figure it out after 2 months. They tried 2 new vlcms and a remanufactured pcm. I tried a used vlcm and a remanufactured pcm. Still no good. I have checked all of the wires on the vlcm harness, and they all check good. I know the vlcm is not powering up, because when I put it on the IDS computer at work and go thru a self test, 3 codes appear that tell me its not activated. If you find out anything, please let me know.

Edit: Sucks not having air conditioning. They somehow hotwired the current vlcm, to get the fan to work.

 

[Psychostang]

Also, I have a used VLCM if you want to try another. Then, at least I'll know if its bad or not.

 

[achesonm8]

I am having a similar problem as this thread many years ago. I replaced the fuel pump and can apply 12V DC to the pk/bk pin and bk pin of the 4 pin male connector and I get fuel up to the rails (tested at the shrader valve). I had already already swapped the fuel pump relay switch before changing out the fuel pump so I don't think the relay is bad. The relay switch has five "pins". Which two are the ones to jump in the fuse/relay box ? My thinking is it may be a bad ground (?).

Other info:

Inertia switch is depressed.
No FDPM with this car.
I am not hearing the new fuel pump cycle on for a few seconds when I turn the key to the first position.
Thanks!

 

[97MarkJA]

Mike, I know on gen 2 cars the fuel pump will only run for a second or two until the PCM sees a run signal. Designed that way so the fuel pump doesn't run the entire time the key is on with the car not running.
Sounds like you have an ignition problem, crank sensor maybe.

 

[achesonm8]

Mike, I know on gen 2 cars the fuel pump will only run for a second or two until the PCM sees a run signal. Designed that way so the fuel pump doesn't run the entire time the key is on with the car not running.
Sounds like you have an ignition problem, crank sensor maybe.

Hi 97MarkJA,

Someone replied! Here is where I am today:

1) New fuel pump installed
2) 12V DC to the pos and neg pins of the first connector, under the car, runs the pump and fuel comes out of the shrader valve on the rails
3) 12V DC to pk/bk wiire connector after the IFS and negative to ground in trunk runs the pump and fuel comes out schrader valve
4) key in on position, voltmeter positive lead to pk/bk wire in IFS connector and voltmeter negative lead to ground in trunk gives a 12V signal

Prior to replacing the fuel pump. I checked all fuses and the fuel pump relay. When I turn the key to the on position I get all the normal bells and whistles and the check engine and oil light are on. When I turn the key to run/start, and the engine is cranking, the check engine light (CEL) goes off. I think this is indicative of the VCRM being OK. I have not looked at the Crank Position sensor. I know where it is on my BMW 850i but not on the Lincoln! Also I will check, again, to see that I am getting 12 V across the first connector upstream from the pump. I am fairly certain, that yesterday I was getting 12V, indicating a proper ground at that point in the wiring. Also I will check the two ground points for these circuits. The VCRM I have not checked yet. It would be helpful to have an EVTM for this car! Anybody know where I can find one? BTW where the heck is the DLC on this car also!...Arghhh!

 

[chris2523]

When I turn the key to the on position I get all the normal bells and whistles and the check engine and oil light are on. When I turn the key to run/start, and the engine is cranking, the check engine light (CEL) goes off. I think this is indicative of the VCRM being OK.

dunno about VRCM, but that does mean the PCM is getting powered up. so part of it is working at least.

i got my EVTMs off of eBay.

 

[achesonm8]

dunno about VRCM, but that does mean the PCM is getting powered up. so part of it is working at least.

i got my EVTMs off of eBay.

Yes, I should order that and the service manual. Crank position sensor I checked this afternoon by checking for a voltage at fuel injector lead. I got about 500 mV. I hooked the pump up directly to the a 12V battery and just let it run for a while. Pushing the shrader valve I have continuous pressure flow of gas to the fuel rail. The car started and ran for about 30 sec. Died and then restarted and ran for about 10 sec and died. Battery had drawn down by this time so it is sitting on a charger now. I am wondering if the replacement pump I bought is not powerful enough but that is not likely. At least I know it is not an electrical issue with getting spark and something to do with the CPS. VRCM appears to be the problem at this point. Thanks!

 

[Bangster]

Yes, I should order that and the service manual. Crank position sensor I checked this afternoon by checking for a voltage at fuel injector lead. I got about 500 mV. I hooked the pump up directly to the a 12V battery and just let it run for a while. Pushing the shrader valve I have continuous pressure flow of gas to the fuel rail. The car started and ran for about 30 sec. Died and then restarted and ran for about 10 sec and died. Battery had drawn down by this time so it is sitting on a charger now. I am wondering if the replacement pump I bought is not powerful enough but that is not likely. At least I know it is not an electrical issue with getting spark and something to do with the CPS. VRCM appears to be the problem at this point. Thanks!

Here are some of the EVTM pages from the 93 manual, and the text from the Fuel System section of the mechanical part:

The electrical system has a fuel pump control relay controlled by the powertrain control module (PCM) 12A650 which provides power to the fuel tank sending unit and pump through an inertia fuel shutoff switch, which is normally closed.

The electrical system provides power to the fuel tank sending unit and pump through two relays: Variable Control Relay Module (VCRM) and PCM power relays. The current path is dependent upon the operating condition(s). When starting and when engine fuel demands are high the fuel tank sending unit and pump electrical supply will be at system voltage. At other times, voltage will be reduced.

When the ignition switch is in the OFF position, the contacts of both relays are open.

When the ignition switch is first turned to the ON position, the PCM power relay is energized, closing its contacts. Power is provided to both the fuel pump relay and to a timing device in the PCM. The fuel tank sending unit and pump runs through the contacts of the fuel pump relay. If the ignition switch is not turned to the START position, the timing device in the PCM will open the ground Circuit 57 (after approximately one second). Opening the ground circuit de-energizes the fuel pump relay (opening its contacts), which in turn de-energizes the fuel tank sending unit and pump. This circuitry provides for pre-pressurization of the fuel system.

When the ignition switch is turned to the START position the PCM operates the fuel pump relay to provide fuel while cranking.

After the engine starts and the ignition switch is returned to the RUN position, power to the fuel tank sending unit and pump is again supplied through the fuel pump relay. The PCM senses engine speed and shuts off the fuel tank sending unit and pump by opening the ground circuit to the fuel pump relay when the engine stops, or is below 120 rpm.

VCRM 1:

VCRM 2:

EEC 1:

EEC 4:

Ignition 1:

 

[DieselDan]

I'd offer some advice, but it sounds like you have hit pretty much everything I was thinking about...

What I can contribute, if you want it is I have the whole 1994 ford EVTM for the MARK in PDF form if you want it.

 

[achesonm8]

Bangster Dude You de MAN! This is really helpful! So I got the car to stay running last night with the pump directly connected to a external 12V battery. The engine was "popping" and sputtering at first. Running roughly but would idle at abt 750 rpm smoothly. So....I will need to digest the material you provided from the EVTM.

Making some progress! I am leaving town tomorrow so I may not have much time today. I am wondering if there is any crossover with Conti's or Merc's for the VRCM...could pop up to my local pull - apart or JY and get one to swap out with mine. Thanks for the help!

 

[achesonm8]

I'd offer some advice, but it sounds like you have hit pretty much everything I was thinking about...

What I can contribute, if you want it is I have the whole 1994 ford EVTM for the MARK in PDF form if you want it.

Thank you for the offer...I saw a thread on here about a group purchase of the PDF file(s) for the EVTM. I probably should pick up my own. If you want to send me one as a gift my email is sacheson@bellsouth.net. Do you like beer? Gift cards for Walmart/Local Brewery are easy to send if I know your snail mail or email address thanks! I am gonna get er fixed!

 

[Adams97Mark]

94m5 just a reminder that when you start car engage gas pedal to floor. This will cause the injectors to be cut off which may help if you flooded the engine by cranking over and over again like I did recently to my 97. Also be sure ignition switch is functioning properly, I replaced my ignition switch and the harness that plugs into it has lots of wires connected to it which maybe causing your car (ignition) issues.

 

[achesonm8]

Definitely the VRCM, removed it and the smell test verified it is toast! I found some very similar and helpfull threads also on LOD which confirmed what I have experienced. I went up to the local pull a part and found a VRCM from a 96 cougar. Real easy to remove it! Brought it home plugged it in and she fired right up and continued to run...I think it is an equivalent VRCM but need to do a little more digging online. Has a similar part number. I will follow up with some pictures. I of course reinvented the wheel. Lessons were learned! My old fuel pump is probably just fine. Will be purchasing a wire piercing probe for future electrical diagnostic work also! Thanks for the help. Pleased as punch! I borrowed these diagrams from another thread. The VRCM could be repaired itself. Here is description of the device.

 

[94m5]

This was quite the thread Necropsy, 2006 till now......


I'm glad you were able to get it figured out. For the record, I can't remember what I did to fix the issue, it's been so long ago.


Mike

 

[achesonm8]

This was quite the thread Necropsy, 2006 till now......


I'm glad you were able to get it figured out. For the record, I can't remember what I did to fix the issue, it's been so long ago.




Mike

Like any well trained scientist/gearhead/car freak I had to use the search function. What did people do before the internet?! Your excused after 8 yrs! I can't remember what I did yesterday. Tomorrow, I will continue my search for a new/used VRCM... At the moment I have "hot wired" the powerful cooling fan. I do not have AC either in the car...I am hot but the engine is not! lol...By the time I get it repaired properly it will be fall and I won't need the damn AC!