No voltage at fuel pump, but relays and fuses all ok - Turbo Dodge Forums : Turbo Dodge Forum for Turbo Mopars, Shelbys, Dodge Daytona, Dodge SRT-4, Chrysler PT Cruiser, Omni and more!
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post #1 of 94 Old 09-12-2019, 09:05 AM Thread Starter
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No voltage at fuel pump, but relays and fuses all ok

Short version:
92 Daytona, 3.0L. Died on me while driving home, now it's parked on the side of a street. Cranks great, but never starts. Poked around with a multimeter yesterday. I'm not seeing voltage at the fuel pump. Rather, I see only a very small voltage, less than 1V, while cranking. I tested this by pulling the connector off and sticking the probes right in. In the PDC every fuse is OK. Tried shuffling relays. The fuel pump relay socket has 12V at the ctrl post, and 12V at the horizontal power post. Even if I try jumping it (horizontal to the opposite vertical) I again see very little voltage at the back of the car.

I'm not really sure how to track this down. Is there a fuse or a fusible link somewhere else? Can it be as simple as a loose connection? I'm gonna go back today with some longer wires for the multimeter and try to figure out which side of the pump circuit is dead. But I don't know where physically on the car are the components in the circuit that are likely to fail.

Longer version:
There's a bit of a history. I had problems with the engine hiccuping or occasionally dying at a light. Replaced the fuel pump, all fuel hoses, fuel filter last summer and *most* of those instances went away. I also suspect my alternator needs replacing, so I thought maybe the hiccups may be misses due to weak spark? Fast forward to this summer, I occasionally hear a buzzing sound coming from the fuel pump. Occasionally takes longer than usual to start, sometimes dies within a couple seconds of starting up but comes right back alive. Now the car won't start at all. Maybe all unrelated, but I'm inclined to think theres some connection.
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post #2 of 94 Old 09-12-2019, 09:38 AM
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Re: No voltage at fuel pump, but relays and fuses all ok

If you have a wsmall battery and some jumper leads and if the pump is working that might get you home so you can work on it there. I am sorry I do not know your car, but if you have voltage at the relay and it is turning on, must be a connection someplace
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post #3 of 94 Old 09-12-2019, 10:05 AM
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Re: No voltage at fuel pump, but relays and fuses all ok

A hillbilly fix might be pull power from a taillight wire and if then fuse holds might get you home then no stress to fix.
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post #4 of 94 Old 09-12-2019, 10:11 AM
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Re: No voltage at fuel pump, but relays and fuses all ok

1)On a 92 Daytona 3.0L power to the fuel pump comes from the Fuel Pump Relay which is located in the PDC.
2)Power into the Fuel Pump Relay is shared by the ASD Relay, the wires split at the ASD Relay and run to the Fuel Pump Relay.
3)Power to both the Fuel Pump and ASD Relays comes from...
Fuse #40 in the PDC on the RD/WT wire.
Fuse #42 in the PDC on the DB Wire.
4)With the key in the "On" position is power present at both of those relay cavities in the PDC?

Post Back with your results.

Jan
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post #5 of 94 Old 09-12-2019, 10:13 AM
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Re: No voltage at fuel pump, but relays and fuses all ok

Forgot to ask...
Are there any fault codes stored in memory?
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post #6 of 94 Old 09-12-2019, 10:24 AM Thread Starter
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Re: No voltage at fuel pump, but relays and fuses all ok

Quote:
Originally Posted by NAJ View Post
1)On a 92 Daytona 3.0L power to the fuel pump comes from the Fuel Pump Relay which is located in the PDC.
2)Power into the Fuel Pump Relay is shared by the ASD Relay, the wires split at the ASD Relay and run to the Fuel Pump Relay.
3)Power to both the Fuel Pump and ASD Relays comes from...
Fuse #40 in the PDC on the RD/WT wire.
Fuse #42 in the PDC on the DB Wire.
4)With the key in the "On" position is power present at both of those relay cavities in the PDC?

Post Back with your results.
All the fuses in the PDC have voltage at a both ends, checked by touching the backs while the fuses still in.

About the fault codes. I can't seem to get the light to flash at anymore. Last time I checked, about a month ago, I has a 12 and a 37. But now I do the on-off-on-off-on and the light stays on solid.
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post #7 of 94 Old 09-12-2019, 10:39 AM
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Re: No voltage at fuel pump, but relays and fuses all ok

You have voltage at the fuses but do you have power at both the ASD and Fuel Pump Relay Power Cavities?

Since you CEL will not flash codes I am betting you lost a power source to the relays and controller.

Check the two power feeds into the relays and post back.
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post #8 of 94 Old 09-12-2019, 04:12 PM Thread Starter
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Re: No voltage at fuel pump, but relays and fuses all ok

My PDC lid doesn't have a "ASD" relay, the relays are 1) IJN. IGN. COIL 2) FUEL PUMP 3) STARTER
ignoring the rad, AC, and WWasher.

So I checked all three. IJN and FUEL were the same layout, with 12V at the 3 o'clock position (12 o'clock being the horizontal, also had 12V) when key ON. STARTER had 5V at the 9 o'clock.

I also fiddled a bit with in the back, and it seems there's a short across the plug. I don't know if this was the original problem or happened while i was trying to backprobe it with paperclips or when trying to disconnect it from the pump. I'll wander the junkyard this weekend for a new one. Maybe thats everything?
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post #9 of 94 Old 09-12-2019, 05:48 PM
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Re: No voltage at fuel pump, but relays and fuses all ok

ALL Chrysler FI vehicles use an ASD Relay.
If your vehicle is a 92 then you have both an ASD Relay and a Fuel Pump Relay.
91 on the other hand did not use a separate Fuel Pump Relay, the ASD handled ALL power feed needs for the + coil, fuel pump, injectors, HO2S,etc.
Starting at the top of the PDC the relays are as follows...
1991
A)Radiator Fan Relay
B)A/C Clutch Relay
C)Headlamp Open/Close Relay #1
D)Headlamp Open/Close Relay #2
E)Auto Shutdown Relay
F)Starter Relay

1992
A)Starter Relay
B)Auto Shutdown Relay (ASD)
C)Fuel Pump Relay
D)Not Used
E)Washer Relay
F)A/C Clutch Relay
G)Radiator Fan Relay

A relay has two separate circuits integrated in the relay housing.
There are four wires, two of which are 12 volt power feeds the others are a ground side control and an output to the device being powered.
The way a relay works is...
Current flows through a winding on the control side and when the controller needs the relay to be actuated it completes the ground internally completing the circuit allowing current to flow. (Engine controllers control grounds, not power)
When current flows through a wire/circuit a magnetic field is created, the magnetic field causes the breaker points/transistor to close on the output side.
When the breaker points/transistor closes power flows on the output side to the controlled device.

Not sure exactly what you are/were referring to when you said...
"I also fiddled a bit with in the back, and it seems there's a short across the plug. I don't know if this was the original problem or happened while i was trying to backprobe it with paperclips or when trying to disconnect it from the pump."

I assume you were at the fuel pump connector and not at the relays.
Even if the connector was/is damaged you can still verify if power is present.
Power at the Fuel Pump Connector is on the DG/BK wire.
Unfortunately starting in 91 you cannot manually actuate the ASD Relay without a scanner so you would need to crank the engine to actually check power at the fuel pump.
If the fuel pump connector was "rock hard" from age and did not want to come off you need to use a hair dryer or heat gun (on low) to heat and soften the connector and it will come right off.

Back to the original question...
Was/Is there 12 volts present at two terminals at both the ASD and Fuel Pump Relay with the key on?

If no unbolt the PDC and physically inspect the underside, it is common for wires to break on the underside of PDC's.

Sending you a PM with wiring so you will have it for future use.

Jan
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post #10 of 94 Old 09-12-2019, 06:41 PM Thread Starter
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Re: No voltage at fuel pump, but relays and fuses all ok

Heres the diagram on my PDC lid:



Is this somehow the wrong lid or is something wacky going on?

But, to your question, yes, there was voltage at two terminals for each relay. 12V for two terminals in each the "inj" and "fuel" relay (as named in the diagram on the lid). 12 and a 5V in the "starter".


As for my not being clear, yes you deciphered me right. Back of the car, at the fuel pump. I got the plug off the pump, and stuck my multimeter leads in each of the two holes of the wiring harness plug. There was continuity between the two. And this continuity went to ground, testing by touching one lead to the frame with the other still in the plug.

Thanks for the wiring diagrams I'll give them a thorough look over tonight, see if I can figure anything out
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post #11 of 94 Old 09-13-2019, 04:23 AM
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Re: No voltage at fuel pump, but relays and fuses all ok

Did you manage to get your car home so you are not working out on the street. Obviously you are in good hands with Naj. I wish you luck. I am trying to absorb your problem and learn.
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post #12 of 94 Old 09-13-2019, 10:53 AM Thread Starter
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Re: No voltage at fuel pump, but relays and fuses all ok

Still in the same place. Its nearby where I work so it's not far from where I am anyway, and it's not a sketchy street, my boss lives a block away. Haven't had the time to come up with a way to jump it yet, but im not above just doing the repairs there.
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post #13 of 94 Old 09-13-2019, 11:23 AM
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Re: No voltage at fuel pump, but relays and fuses all ok

Chrysler named your ASD Relay the "INJ/Ign Coil"Relay which kind of makes sense since they are the components that are being powered through that particular relay.
When I was a Chrysler Tech (1995-2010) we ran into the "what is it called" issue on occasions, what the service manual called a part and what the parts catalog called the same part where not always the same so if it was not a common part the people in the parts department could not find it.
I would have to bring them the service manual to show them the part I wanted.
You would think that the people writing the FSM and the Parts Catalog would communicate with each other, but NO.

If you are going to be doing your own work and reading manuals you need to understand...
Wiring and Service Info may not always be correct to what is actually on your vehicle.
The manuals are written before production begins so changes may be made on the assembly line or mistakes may be made in writing the manuals so you need to realize this when looking at the info if something does not make sense.
Chrysler used to send out (when they still used paper catalogs) service manual page corrections to all of their dealers as techs found and reported mistakes in the manuals.
The corrections page was sticky on one side and placed over the incorrect page in the manual.
Since all dealers/manufacturers use online service manuals now making corrections is much easier.

Now onto your issue...
If you had/have two power sources at both relays but no power at the fuel pump connector then you need to verify power output on both relays (you will have to test on the underside of the PDC or tap into the output wire at each relay and test with the engine cranking).
I recommend using a 12 volt test lamp so you can see it from inside the car while cranking the engine.
Once you know if you do or do not have power output from both relays we can move on to further diagnostics.
ASD Relay (INJ/Ign Coil) Power Out - DG/OR Wire
Fuel Pump Relay Power Out - DG/BK Wire

As far as your tests at the fuel pump connector...
Checking continuity between the two terminals at the fuel pump connector is not a valid test since you are going through the entire circuit.
At the fuel pump connector
DG/BK (Dark Green/Black) is Power.
Power will only be present with the engine cranking/running.
There should not be continuity to ground on this wire.
BK(Black) is Ground.
This is a body ground located on the Left (Driver Side) Quarter Panel.
You will/should have continuity to ground on this wire.
(Be sure you do not confuse the two)

To test the fuel pump power/ground circuits at the fuel pump connector place your meter on a 20 volts scale (or use a 12 volt test lamp connected between the two terminals), probe both wires (DG/BK with + and BK with -) and crank the engine.

Just a Note/FYI.
(When probing a connector terminal be very careful not to spread/push out/damage the terminal in the connector, that is why it is recommended to backprobe.
If you do need to test at the terminal itself it is suggested you just touch the probes to the terminal, not push them in.)

If 12 volts are present then both power and ground circuits are Good.
If 12 volts are not present then we need to determine if this is a power or ground issue which is what we are in the process of doing.

Jan
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post #14 of 94 Old 09-14-2019, 02:18 PM
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Re: No voltage at fuel pump, but relays and fuses all ok

Are you making any progress? Naj is away I believe. I have had 3 pump failures in the wife's GM suv and had no choice but to flatdecked everytime. Told not to run less than 1/4 of tank as the fuel is too hot and the pump cannot cool. If you have a battery and you jump the pump and it works you should be able to get home. Please keep us posted.
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post #15 of 94 Old 09-15-2019, 05:34 PM Thread Starter
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Re: No voltage at fuel pump, but relays and fuses all ok

Heres the update so far. Im equal parts feeling like im making progress and feelingling like my understanding of how this works is entirely wrong.

I think I mentioned earlier that I detected continuity between the two prongs of the plug, back at the fuel pump. This is with the car off, and boh the fuel pump relay and the ASD relays removed. This seemed pretty wrong to me, and thought it might have been the plug itself. I got a replacement at the junkyard, but it seems the plug itself isnt the culprit. But this did give me an opportunity to take inspiration from Rampageproject and try to hotwire the pump. I ran my jumper cables from the battery back to the exposed ends of the cut plug wires. And this gets the pump to pump, or at least to make noise, which is more than i got before. But cranking the car didnt start it. I'm gonna put some more gas in it, even though im just below a quarter tank according to the gauge.

I'll try to post another update tonight after i add some gas.
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