Electrical / Power issue to fuel pump

[OutOfTime]

Let me preface this post by saying that when I bought my Delorean, the previous owner was in the process of swapping out the fuel pump, so I dont know what the original problem may have been, but Im thinking it was more electrical than the pump itself...

I attempted to install a new SpecialT fuel pump today and discovered an electrical problem that is likely the real culprit to the fuel delivery. After the installation pump was complete (and a long list of troubleshooting steps to identify why it was not turning on) I discovered that the Black/Purple and White/Purple power wires that plug into the fuel pump are only delivering about 1 Volt of power. (My battery is brand new) Also, power is only being sent to the pump while the key is turned and the engine is cranking (not sure if thats normal or not).

When I bench tested the pump to 12V source it ran perfectly.

Anybody know of any common problems that would cause just 1V of power voltage to my fuel pump? How would you recommend I start trouble shooting this?

Thank you

[Ron]

Measure them separately so you know if you have a bad feed or bad ground. IE Go to the battery with one lead....

[sdg3205]

Do you have a white dot inertia switch?

[DMC5180]

Pull the RPM relay and perform an audible continuity test between the FP connector and RPM connector terminals of the white/purple wire. You will probable need to rig up an extended wire lead to span the distance.
Their is one front harness to main harness connector located inside the underbody with the washer fluid tank removed. You may have a poor connection at that connector. Green corrosion syndrome. If you don't get an audible tone it will be due to high resistance. The black/ purple wire should also be continuity checked to ground.

[Ron]

A little more to work with

I.E. Go to the battery with one lead:
Plug should be disconnected.
Ground- Black tester lead to B/P, Red tester lead to Battery (+).
Feed- Red tester lead to W/P, Black tester lead to Battery (-).
Tester should read at least 12V+ each.

If you don't have a good ground, you might try resetting the inertia switch.
You could temporarily ground the B/P wire (this defeats the safety switch, so remove the ground after testing!)

If you don't have a good feed, try removing the RPM Relay then jumper the W/P in its socket to the N (Brown) wire (they are in opposite corners, diagonally)..... This should make the pump run even with the key off.
Yes it is normal for the pump to run only when the engine is turning on some cars. I.E. Some will prime, some don't, etc...

Let us know what you get......

[Ron]

YO, Dennis!
:hihi2:

[Bitsyncmaster]

For finding a bad connection, you need to leave the load (pump) connected. You will need to make a short jumper with two 1/4" flat pins which you can buy at most auto parts stores. Use 16 AWG wire or larger. You pull the RPM relay connector and plug one end of that jumper into the white/purple wire pin. The other end goes into the brown wire pin. That should power your pump without turning the key on.

Now as Ron suggested, use the battery negative terminal as the meter reference (meter black lead). Then measure the fuel pump terminal white/purple lead with the meter red lead. You may need to make up a meter lead extension via some wire and a few alligator clips to reach both of those connections. You should read almost 12 volts. If so, your problem is in the ground side.

Now move the meter red lead over the pump terminal with the black purple wire. You should read almost zero volts. If so, your problem is in the +12 power side.

Remove the jumper and report your findings and we will help you troubleshoot further.

[OutOfTime]

Thank you all so much! I'm going to run these tests and report back. I'm not much of an electrician, so I may end up asking some additional questions.

Mark

[DMC5180]

YO, Dennis!
:hihi2:

Hey, Ron ! Yeah just a bit of insomnia to be up at that hour. 😜

[OutOfTime]

Test update:

I brought a 12V battery to test the white/purple and black/purple wires, and the results are perplexing...

White/Purple read .4V when connected to battery ground
Black/Purple read 0V when connected to battery ground

Seems to me like maybe a rat or something chewed through this wire, these numbers look horrible... should I start tracing the wire back? If so, any suggestions on how to access it, it runs right under the spare tire holder.

Thanks again guys

[DMC5180]

Use the Ohms/continuity function on your meter and test the wires like I mentioned earlier. Let us know the number results.

[OutOfTime]

Use the Ohms/continuity function on your meter and test the wires like I mentioned earlier. Let us know the number results.

Sorry, I somehow missed that, I'll give that a try and report back.

[OutOfTime]

Pull the RPM relay and perform an audible continuity test between the FP connector and RPM connector terminals of the white/purple wire. You will probable need to rig up an extended wire lead to span the distance.
Their is one front harness to main harness connector located inside the underbody with the washer fluid tank removed. You may have a poor connection at that connector. Green corrosion syndrome. If you don't get an audible tone it will be due to high resistance. The black/ purple wire should also be continuity checked to ground.

OK... now Im really confused....

I put on the jumper and still no power to the FP.

I tested the continuity off the white/purple wire expecting there to be none... but wow, there was continuity! So now I know the connection is there, but why isnt it being supplied with 12V?

Thanks again guys, you are awesome

[DMC5180]

What was ohms reading. Use auto range if you have it. Also do the black/purple at the FP connector to any ground.

[OutOfTime]

What was ohms reading. Use auto range if you have it. Also do the black/purple at the FP connector to any ground.

Ohms reading was 1.0 when at the 200 level.

There is NO continuity to ground, I ran that back all the way to the battery just to be sure.

[OutOfTime]

For finding a bad connection, you need to leave the load (pump) connected. You will need to make a short jumper with two 1/4" flat pins which you can buy at most auto parts stores. Use 16 AWG wire or larger. You pull the RPM relay connector and plug one end of that jumper into the white/purple wire pin. The other end goes into the brown wire pin. That should power your pump without turning the key on.


Ok, update... I left your jumper on and ran a test ground wire to the battery and plugged the connector onto the fuel pump. It instantly came on :cool:

So it seems like I have a bad ground wire.... the question is, can I run a new ground wire from the FP to an anchor point in the front trunk and call it a day? Thank you

Mark

[DMC5180]

Test the voltage of the brown wire at the RPM relay connector too.

[OutOfTime]

Test the voltage of the brown wire at the RPM relay connector too.

When I tested the voltage between the brown wire and the white/purple I got a reading of (-3.40) ... Now I'm really confused but that doesnt take much

[DMC5180]

Just do a simple voltage check of the brown wire. Do not run through the white/purple. We're just doing basic verifications.

Post a photo of your relay/fuse compartment And your ohm meter connected.

[OutOfTime]

Just do a simple voltage check of the brown wire. Do not run through the white/purple. We're just doing basic verifications.

Post a photo of your relay/fuse compartment And your ohm meter connected.

Im sorry, Im a total newb at this.

When I connect one probe to the brown wire and the other to the + battery terminal I get 0.00. To the negative terminal I show -12.65

Mark

[DMC5180]

Okay your showing negative so reverse the leads.

[Ron]

Hey, Ron ! Yeah just a bit of insomnia to be up at that hour. Yeah...I was up and posted at the exact same moment for the same reason...

Seems you missed my P.M. on something I wanted to bump heads on...??

======

And NOW, back to our regularly scheduled program...

[Ron]

Im sorry, Im a total newb at this.
...
$.02

Don't feel anything negative!!!
You have three people telling how to do it and all are good ways, but different...confusing.
Pick one (the one you understand the most or are deepest into so far, ?Dennis' me thinks?...

[OutOfTime]

Okay your showing negative so reverse the leads.

Yup, so brown to ground I show 12.65.

Is it safe to run a new ground wire and install pump?

[Ron]

can I run a new ground wire from the FP to an anchor point in the front trunk and call it a day? Thank you.


NO!:


You could temporarily ground the B/P wire (this defeats the safety switch, so remove the ground after testing!)

[DMC5180]

Yup, so brown to ground I show 12.65.

Is it safe to run a new ground wire and install pump?

Not so fast, now do the next step I mentioned a couple posts back.

So far you have not confirmed 12V at the FP connector (unplugged).

[OutOfTime]

So far you have not confirmed 12V at the FP connector (unplugged).

Yes, with the jumper in place I get 12.6V on the FP power.

[DMC5180]

Okay now we're getting someplace. Did you do a continuity/ohm test of the black/purple wire at the FP connector to a ground. The head of the underbody bolt in the trunk is easy spot to get a ground for continuity.

[OutOfTime]

Okay now we're getting someplace. Did you do a continuity/ohm test of the black/purple wire at the FP connector to a ground. The head of the underbody bolt in the trunk is easy spot to get a ground for continuity.

I did, and there is NO continuity. The FP black/purple is dead.

[DMC5180]

Okay, go to the inertia switch and probe both ends of the black/purple wire connectors ( disconnected).

Also cycle the switch while your at it. Lift the plunger and push it back down.

Dennis

[OutOfTime]

Okay, go to the inertia switch and probe both ends of the black/purple wire connectors ( disconnected).

Also cycle the switch while your at it. Lift the plunger and push it back down.



Well I found the problem... LOL There is NO inertia switch! Looks like a long time ago the previous owner cut it off. See pic:

35812

Theres my black/purple wire....

So heres my plan, tell me your opinion. I will run a new ground wire and install the FP, as Im on step one of probably 100 before I drive the car. I will order a new inertia switch from SpecialT and rewire it up before I drive the car.

Thoughts?

[DMC5180]

I'd say that's an appropriate plan at this point. I'd be curious as to where the fused wire is running from that red scotch lock wire tap. I'd guess it has nothing to do with the inertia switch wiring though.


Actually for now you can just connect the black/purple to the black ground wire with a temporary jumper like what you used for the rpm relay socket. Just wrap the terminals to protect from inadvertent contact with a live wire.

Confirm that you now have good continuity to ground via the FP connector B/P wire and move on to your next issue or FP installation.

Btw: I was not aware Hervey carried inertia switches, I figured you get that from Toby.

[Ron]

Well I found the problem... LOL There is NO inertia switch!
:p

=======

DENNIS,

I can't send you the pic requested...."DMC5180 has exceeded their stored private messages quota..."

[DMC5180]

:p

=======

DENNIS,

I can't send you the pic requested...."DMC5180 has exceeded their stored private messages quota..."

Let me clear some space. Funny I did not get a box full notification.


Space cleared and I got your PM. That was an interesting one.

[dmruschell]

The ground location that the fuel pump circuit connects to is shared by a few other things. On the recommendation of a few other posts (and the fact that the ground side of the fuel pump circuit on my DeLorean stopped working), I connected the ground side connection of the inertia switch directly to the frame on both of our DeLoreans. I used the frame mounting bolt below the center console in the driver's side footwell.

[OutOfTime]

Update...

I rigged up the ground and reinstalled the fuel pump. It primes and acts fine. I replaced the fuel filter after, while I was under the car and can verify that it was full of fuel (that was fun).

The problem is that it will still not start. It doesnt even attempt to start, as if the fuel is not reaching the engine, but everything checks OK up to the distributor. I know that I have spark, as the engine will run as long as fuel is being poured into it from an outside source.

My question is, where should I go from here?

[DMC5180]

Do you have resistance on the air metering plate?

[OutOfTime]

Do you have resistance on the air metering plate?

No I do not.

[DMC5180]

You need to jumper the rpm relay to to force the pump to run. Then check for Rest pressure resistance on the air plate. Is the air plate up or down at the moment?


Dennis

[OutOfTime]

You need to jumper the rpm relay to to force the pump to run. Then check for Rest pressure resistance on the air plate. Is the air plate up or down at the moment?


Didnt know I had to jumper the pump at this stage, but I will do that. Air plate is up at the moment, making light contact with the housing.

[DMC5180]

Didnt know I had to jumper the pump at this stage, but I will do that. Air plate is up at the moment, making light contact with the housing.

Plate up is good. You may want to pull the injectors and place them in small jars. This would really allow you to see what is happening when you press the air plate.

Do you know about how long the car has been sitting?

[OutOfTime]

Plate up is good. You may want to pull the injectors and place them in small jars. This would really allow you to see what is happening when you press the air plate.

Do you know about how long the car has been sitting?

The car has been sitting for about 5 years. I uploaded a video to youtube of trying to start it just now, with the relay jumped and FP running. It seems like it tries to start for just a second, then dies.


https://www.youtube.com/watch?v=vLU4B_0yF2g

[DMC5180]

Sounds like it started on the Cold start fuel. You may have air in the injector lines that needs to be purged out. So far what I see, your on the right track. Some times it takes a few attempts before it will stay running.

[David T]

Sounds like it started on the Cold start fuel. You may have air in the injector lines that needs to be purged out. So far what I see, your on the right track. Some times it takes a few attempts before it will stay running.

Check that you did not mix up the feed and return lines at the fuel pump.

[OutOfTime]

Sounds like it started on the Cold start fuel. You may have air in the injector lines that needs to be purged out. So far what I see, your on the right track. Some times it takes a few attempts before it will stay running.

I pulled the passenger side injectors, cleaned them up, and tested them each. They are all spraying a satisfactory level. Tested a start before I fought with the drivers side injectors and no change on the start problem. Sounds identical to the video posted above. Frustrating! (Yes I know, welcome to DMC ownership)

[DMC5180]

Try some gas pedal when it fires on the cold start.

Is the rpm relay jumped or do you have the relay installed?

Confirm your ISM is vibrating with the key in the run position.

Dennis

[DMC5180]

Every time you press the plate to check for injector flow of one injector, you are running fuel through the other injectors still in the engine Flooding those cylinders. This is why it works best to pull all injectors at once for flow checking simultaneously.

If you think the engine is flooded press the gas pedal to the floor while cranking to clear it out. The engine should fire eventually puking out black smoke as it clears.

[OutOfTime]

If you think the engine is flooded press the gas pedal to the floor while cranking to clear it out. The engine should fire eventually puking out black smoke as it clears.

It started! I have the relay back plugged in and was able to fire it up with a little gas. I have the video attached below. It will stay running as long as I keep the RPMs over 2000 or so... as soon as I lift off the gas it dies, which is what it does in the video below:


https://www.youtube.com/watch?v=uaks22Z127I

Considering where I started this is great progress, and I owe a huge thanks to DMC5180. Besides cleaning the rest of the injectors and running the engine a bit more, what would you recommend the next step be?

Thanks!!

[DMC5180]

Did you verify the iSM is operating? Sounds like it's loading up. Did you you experience backfiring when the engine was stumbling?

[OutOfTime]

Did you verify the iSM is operating? Sounds like it's loading up. Did you you experience backfiring when the engine was stumbling?

No backfiring. How would I test to see if the idle speed motor is operating? Thank you

[DMC5180]

Is it buzzing when the key is in the run position? Put your hand on it.

If it's buzzing, you next want to verify the valve isn't stuck. You check it by swinging the CS pipe towards you as far as it will go (1/2" or so) and removing the short connector hose from the ISM spigot. You should be able to push the hose aside enough to be able look in the spigot opening with a flashlight. Then turn the key to the run position and watch the valve. It should close then open over about 10-20 seconds.


Dennis

[OutOfTime]

Is it buzzing when the key is in the run position? Put your hand on it.

If it's buzzing, you next want to verify the valve isn't stuck. You check it by swinging the CS pipe towards you as far as it will go (1/2" or so) and removing the short connector hose from the ISM spigot. You should be able to push the hose aside enough to be able look in the spigot opening with a flashlight. Then turn the key to the run position and watch the valve. It should close then open over about 10-20 seconds.


Dennis

Yes, it is buzzing. Confirming this little hose is what you are saying to remove and look inside:

35852

[DMC5180]

Yes


Dennis

[OutOfTime]

You should be able to push the hose aside enough to be able look in the spigot opening with a flashlight. Then turn the key to the run position and watch the valve. It should close then open over about 10-20 seconds.


I turned the key to the run position and was able to observe the valve slowly close, however it did not reopen, it stayed closed. Is that normal?

[DMC5180]

Your really just confirming that it moves and is not stuck in the closed position. You should be Good.

I run a DM eng idle ECU, so mine cycles differently that the stock ECU. My ISM pops open 50% after about 3 seconds of being fully closed.

Every time you cycle key the ISM fully open first?

[Bitsyncmaster]

I turned the key to the run position and was able to observe the valve slowly close, however it did not reopen, it stayed closed. Is that normal?

I think that is normal for the stock idle ECU setup. It should quickly pop about half open when your first turn the key on then slowly close or open fully. I can't remember which way it went.

[OutOfTime]

Still no idle... What is the standard setup for the idle microswitch? Its pressed down completely now, I have to press the gas (or twist the throttle control) to get it to "click". Is that proper?

Thanks

[DMC5180]

Yes, that is normal operation. As long as the switch is down when the throttle is released, the ISM ECU will be energized and controlling the ISM.

It may be time to start looking for potential vacuum leaks. Review the routing chart on the underside of the engine cover. It's also possible the CO adjustment is way off. I noticed you have the removable CO plug. Who knows what the PO did considering your inertia switch was gone.