Engine/Transmission (1994 - 1998) power to fuel relay....none

[TSPowell]

I have an ongoing post on here about not starting... still haven't figured it out yet, but this is just about the relay and solenoid.



I ruled out the solenoid a while ago, it operates fine. So, I was going to order a new relay from LarryB's, but I went out with a test light first, results:



I have power with the key off to the load circuit side of both relays (fuel shut-off & fuel heater) like I should, and nothing on the control circuit, because the key is off. With they key on, power comes on to the control circuit side of the fuel heater but not the shut-off relay.



So the fuel heater works fine but Im not getting power from the key to the shut-off relay on the control side. Therefore the relay might be just fine, but I cant get power to it, to close the load side.



ANYTHING WOULD BE GREAT!!!

I dont know much about electronics.

 

[Joe G.]

Take a close look at the blue wire on the positive post of the driver's side battery. It may be broken, loose, or corroded. It's a fusable link. The wire color changes at a splice before it goes to the fuel solenoid relay.

 

[TSPowell]

Take a close look at the blue wire on the positive post of the driver's side battery. It may be broken, loose, or corroded. It's a fusable link. The wire color changes at a splice before it goes to the fuel solenoid relay.

I've got power after the fusible link, its good

 

[Joe G.]

So the fuel heater works fine but Im not getting power from the key to the shut-off relay on the control side. Therefore the relay might be just fine, but I cant get power to it, to close the load side.

If I understand the above correctly you are saying you are not getting power to the relay 12 volt source to connect to the load when the relay is closed. If that is a correct reading and you have power to the blue wire then you have a broken connection. Try using a jumber from the positive post of the battery to the relay on the 12 volt source pin.

 

[TSPowell]

No, the 12v source to the relay is fine. Im not getting the power from the ignition switch (control side) so it can close the relay, which would complete the circuit (load side) to the solenoid.



Maybe this is better: I have the power to operated the solenoid, I cant get the power from the ignition switch to close the relay so it can operate the fuel shut-off solenoid.

 

[McLaughlin]

Not sure if this will help but here is a schematic I put together of my 97's wiring. I had/have a problem very similar to yours I either had/have a problem with corroded connections on the plus drivers side terminal or low battery voltage/current under load(when starting). Seems most of the connections on the terminal were very bad although visually they didn't seem to bad until I took them off the terminal and the connection between the batterys was so bad the second battery was essentially "off-line". My truck would sometimes start and sometimes it wouldn't (about once-a-day). When it didn't start the solenoid wouldn't pull up just like yours. Like you I also saw voltage at the output of the fuseable link before I cleaned the terminal connections.

 

[Joe G.]

Ok, (assuming that the starter is cranking) according to my '95 service manual (agrees with the above diagram mostly) the circuit from your start motor relay is a brown wire. It goes to splice 113 to pin 2 of connector C173 which is the connector for the fuel solenoid relay. Now to make sure that you don't have 12 volts on that pin you should pull the relay and put a meter test probe in that pin socket. Then run the starter and see what you get. If nothing then do a continuity check between that pin and the output of the starter relay.



There are about three pages involved with this circuit. If you don't have a '95 service manual I can scan the pages and e-mail them to you.

 

[1tuffram]

I have an ongoing post on here about not starting... still haven't figured it out yet, but this is just about the relay and solenoid.



I ruled out the solenoid a while ago, it operates fine. So, I was going to order a new relay from LarryB's, but I went out with a test light first, results:



I have power with the key off to the load circuit side of both relays (fuel shut-off & fuel heater) like I should, and nothing on the control circuit, because the key is off. With they key on, power comes on to the control circuit side of the fuel heater but not the shut-off relay.



So the fuel heater works fine but Im not getting power from the key to the shut-off relay on the control side. Therefore the relay might be just fine, but I cant get power to it, to close the load side.



ANYTHING WOULD BE GREAT!!!

I dont know much about electronics.

was there ever a solution to this problem because it is exactly what I'm dealing with right now. Myself and Larry B thought it was the fuel shut off relay so I replaced it to no avail. I'm having the same problem of no voltage at the brown wire, pin 85 on the relay harness with the key on. I have 12. 6 volts at pin 30 with key off or on. Following the testing procedure from my 1995 factory service manual I've tested my OEM fuel shut off relay, Larry B's relay, the fuel heater relay, and several of the relays in the PDC box (starter motor relay, etc) and all are fine. I have tested continuity on the fuel shut off Solenoid as outline in my Cummins service manual and the pull / hold circuits fall within parameters. I can get the "pull" circuit to engage the solenoid if I use a jumper wire between pin 30 and 87 at the fuel relay wire harness connector (as Larry B suggested), the hold circuit will hold the plunger up so I doubt the solenoid is bad, relays all test fine, and the blue fusable link is good. My battery connections are clean and tight. The blue fusable link wire changes to a red with black stripe wire after the fusable link and I'm ASSUMING it is the same red/black stripe wire which ends at pin 30 on the fuel relay... which I have 12. 6 volts at. The factory service manual wire schematics don't really mention the fusable link but the wire diagram shows a red/black wire going from pin 30 to the "fuel shut down feed" at the positive battery terminal. I spent 20 minutes troubleshooting this with John at Larry B's to no avail. It was suggested maybe I have a bad wire or connection somewhere.



Eventhough the starter turns over just fine (and the truck will start providing I manually pull the fuel solenoid plunger up which then the "hold" circuit will keep it in the up position), could I have a problen in the starter/solenoid??? According to the wire schematics the Brown wire I'm not getting power to is tied into the starter motor (the starter motor relay in the PDC tests OK and I'm getting power at that relay). I've never had a hint of any problem with the starter so far, but I did order the starter contacts and plunger from Larry while I was at it since the truck has around 97,000 miles. I don't think the starter contacts are the problem..... but the brown wire at the starter solenoid I believe is part of the same circuit and brown wire at pin 85 on the fuel relay connector.



Any suggestions are welcome

 

[Howard Durand]

Looking at the schematic for the starter circuit, the brown wire at pin 87 on the starter relay splits as it comes out of the power distribution center. One leg goes to the starter solenoid, which is working correctly. The other leg goes to the fuel shutdown relay, which is not. It would appear there is a bad connection or broken wire somewhere between the engine starter relay pin 87and the fuel shutdown relay.

It is also possible that you have a grounding problem at the fuel shutdown relay.

 

[1tuffram]

update

This morning I decided since all the relays, solenoid and fuseable link tested fine then I must have a bad wire or connection. Looking over the wire schematics I decided to further investigate the brown wire path. After the PDC and starter motor relay there is 1 splice (s113) and 1 connector (c125) before the fuel shut down relay connector (c173). I started with the easiest with was the brown wire at the fuel relay, but was unable to remove the wire and spade plug from connector 173 to fully inspect the wire and crimp. The connection appeared solid with all the tugging and pulling I was doing and could not really see any burning, corrosion, etc where the wire was crimped. I next found c125, which is located on the drivers side firewall between the clutch fluid reservoir and the hood hinge right above where all the mass of wires enter the cab. 3 connectors are mounted there (grey, dark grey and black), c125 is the grey one. I took it apart and did not notice anything suspicious by looking at the pins/sockets of the male and female ends. The brown wire seemed to be solidly secured after tugging on it. Since the factory service manual shows splice (s113) to be so conviently located somewhere inside the wire harness near the PDC and needing to remove the driver side battery to gain access... I decided to stop and see if I made any progress.

I started to think about a reply Joe stating the key needs to be in the start position to get power at the fuel shut off relay. So I hooking up my multimeter and cranked the engine over and got around 10. 5 volts. I did not try this yesterday, so now I'm wondering if fiddling with the wires at the connectors did something. So I decided to plug the OEM fuel relay back in and see what happens and much to my surprise the truck started. Not exactly sure now what the problem is/was, I'm assuming maybe a bad connection at c125 since that is basically the only new thing I messed with today, hopefully the problem is solved but I'm not going to count on it. This may be one of those intermitent things..... maybe a loose wire connection or a pin not making a good contact connection in one of the connection plugs.



I decided to install Larry B's starter contacts and plunger, good thing I did. The one contact was worn down to paper thin and severly pitted!!!