Fuel pump relay?

I would swap out the fuel pump relay. here is the location so you can make the swap to see what happens. You can use this guide to test it as well.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit


Check out the images (below). Please let us know what happens.

Okay, attached you will see the wiring for the pump. Dark Green w/white stripe at 85 should have power during prime and then in run. 86 runs to ground through black with white stripe. It triggers the relay on. Pin 87 should have power from fuse 9 ECM BATT on the orange wire and pin 30 takes that power and sends it to the pump. You say the prime wire will power the pump, which should mean the circuit from 30 to the pump is good as it uses the same wire.
If jumping to 87 doesn't power the pump, then I would start at the fuse. Then if it's good but no power to the socket itself go to the oil pressure sender and find the orange wire on it, check it for power. If it has power but 87 has no power, then you will want to look at the wiring under the relay center. If there is no power at the switch the problem is between the instrument panel fuse box and the relay center.

Wow,

Steve W, thank you for the well thought out and easy to understand explanation. I need to thank everyone here at 2CarPros because, except for the oil pressure sender, I was actually able to come up with that same answer by reading a bunch, excuse me, I mean a bunch, of questions and answers provided here. Can’t thank you enough because although I did come to that “conclusion “, for me it was literally just theory as this particular issue has taken me at least two grades above my pay scale, lol. By oil pressure sender, I’m assuming you’re referring to the unit behind and below the distributor by the firewall. I’ll let y’all know.
Thanks again

Fuse 9 (ECM/batt) and 10 (ECM/ign)both have power. I checked them earlier, haven’t checked oil pressure sender yet, although I do remember trying to start it with it unplugged and it didn’t help, but I will test properly ASAP.

Ken L, thank you very much, I’ve tried switching them, tested all for functionality and all did, even bought a new one. I did notice the middle relay doesn’t and hasn’t been working I assume since I got this truck a few years back when I was told the horn didn’t work. I have never looked at it since. I don’t know if this is related at well but when I bought it, I was told not to use cigarette lighter because somehow it drains the battery excessively fast, I don’t smoke and never used it, just remembered that actually. I doubt it’s related to my fuel pump problem, but every little bit of info can’t hurt when diagnosing.
Absolutely amazing job y’all do just with the info you’re given, never seeing or touching the vehicle and making it happen. I guess that’s what happens when you’ve lived it every day, thank you all again for your time and expertise.

Yes, that is the sender. The fuel system on those is typical of that year GM. You turn on the key and the relay trips and primes the fuel system. Once the engine starts and produces oil pressure the oil pressure switch takes over to power the fuel pump. That way if something happens like a rollover the oil pressure drops and the engine shuts down due to no oil pressure. In your case you mentioned it didn't prime when the key turned on so that could be the relay or pump wiring. Then if you fixed that and then found it would start and run for a bit but not stay running, I would look at the oil pressure sender as it is what keeps it running. Another item about the oil pressure switch would be that if you try to start the engine and it cranks a while and then starts and runs it could be the relay circuit as the oil pressure switch finally closed from the oil pressure and powered the pump on.

Okay, finally got to check orange wire at oil pressure switch, with wire to ground it lit a test light and with voltmeter wire to ground it had the same voltage as the battery. I retested the fuse box, so we’d have accurate results and both fuses 9 and 10 are good, I tested the fuse plugs. #9 key off 12.8 top leg.
12.3 bottom leg
#9 key on 12.3 top leg
0.23 bottom leg
#9 with fuse in top 12.25
Bottom. 12.20
#10 key off top leg 0.0
Bottom leg 0.0
Key on top leg 11.7
Bottom 1.17
#10 with fuse in key on
11.7 top and bottom .
So now I need to reread what you said so I know where to go, I believe it was check wires at relay center. Can you give me your best advice on how to access them? I’ve got the glove box out and a good bit of the dash and it still looks ridiculously difficult if I have to run a new wire from relay center to fuse panel that’s for sure, especially considering I’ve never tried before, not scared of it just would love some experienced guidance.
Thank you

To install it nicely you should be able to reach up to the relay box and slide it off the metal tab and bring it down to get to it. The fuse box end is a bit harder, but you remove the two screws in the opening and then the box drops down, the hard part is usually snaking it through the other harnesses. Testing looks like the power is there, just not getting where it should go.

Just so I’m not doing extra work, pull the wire going from fuse box to relay center if I don’t see anything obvious at the connections?
Thank you

I've seen a lot of wires broken right at the connectors. It's like they crimp them on, and the wire fails right at the connector. However, if you cannot find anything you could run a jumper wire across the floor for testing.

Thank you, man, I look forward to letting you know. While looking for any other issues related to this I noticed my crack sensor wires were getting exposed at the sensor so I picked up a new one today but it’s raining so I’ll get it in tomorrow.

No rush, I'm familiar with "open air" shop work. LOL

That’s awesome !!!

Question, would rewiring my crankshaft sensor with a new pigtail cause my ICM to not send spark to coil? ICM wired (white/black stripe) has power with key on but doesn’t flash when cranking, it just goes off.
Do I need to do a relearn on crankshaft sensor, battery was not hooked up when I was changing wire pigtail?

If the sensor is known good, it could cause a problem if it wasn't correct. The purple wire is the sensor ground, the pink wire is 12 volt power and the yellow is the signal wire.
At the ICM you have the black wire as a ground, the white/black wire is the tachometer signal the white is the timing signal and pink is 12-volt power.

Thank you, I’m sorry I had this thread take this turn, boy am I sorry, I should’ve just left the stupid crank sensor alone. Now I have most of the dash taken apart and haven’t been able to get to it and no spark now also. It looks like my coil isn’t receiving signal from ICM (the thing right next to it) although both are getting power and have ground, I wasn’t able to test the crank sensor signal by myself, the only way I know was to disconnect coil to distributor(so it doesn’t start) and test the signal wire by piercing and turning the crank by hand. Well, I started to, had everything ready, couldn’t get past the compression without an extension on my socket wrench and when I got topside, I hadn’t even hooked ground wire up, threw my tools into the yard and grabbed a beer. I’ll test it later.
Thanks again man, you’re a voice of reason in this storm of diagnostics.

Well, glad to have last night behind me. Figured I’d go back to my original problem, take it from there. I have continuity from the only wire connected to fuse 9 (orange) to the relay center where the fuel pump relay plugs in. There are 5 wires connected to the spot relay plugs in with red in the middle spot and I’m assuming it goes to the fuel pump test terminal under the hood, drivers' side. I have continuity from PCM to relay center in glove box. I guess I need to check continuity from black and white wire between relay and pump and if any other color goes to pump as well. Once again, thank you for the help.

Both pics are of the fuse box spot 9.

The red wire will be the prime wire, basically it is there to bypass the relay in test cases, like if you needed to pump out the tank or test the wiring and can be used to run the truck if the oil pressure switch fails. The power between the relay and the pump will be the gray wire, it is also the power from the oil pressure switch.
In your picture test the orange wire, which is the output from fuse 9. It sends power from there to a splice (222 in sch) where the power splits with one leg going to the pressure switch and the other to the relay.

The orange wire has the same voltage the battery, actually it does in the fuse box and the relay.

Before I lost my spark, the fuel pump and truck would run when giving battery power to the red wire.

That shows that the gray wire from the relay out to the pump is okay. The orange wire should run to the relay at pin 87 and out to the oil pressure switch with that same voltage.
The power to the pump should only come on for a couple seconds when the key is first turned on, if it does the relay, isn't the issue. A quick way to test the oil pressure switch feed is to simply jump the pins with the orange and gray wires, if the pump runs the wiring is good. If that works but it doesn't come on at all when you turn the key, then there is an issue on the relay side. Your testing already said it didn't prime, but that you did have power at the oil pressure switch. Correct? If that is the case and there is no power at terminal 87 on the relay, then that branch is the problem.

Yes sir, the oil pressure switch was getting the same power.

Well shoot, this wasn’t happening before but jumping orange to grey does make the pump come on!

Still doesn’t come on with key though.

Well, at least it's some progress. Go to the relay socket and see if there is now power at terminal 87. It's unfortunately very possible it is nothing but a loose connection in the relay box or the wire to terminal 87. Chryslers are well known for bad connections.

Yes, there is power to 87 which is orange.

I thought I checked them all but I’ll be happy if one was loose.

And now power is out to the neighborhood here in Florida, so I’m temporarily shut down.
Thank you again.

Okay, get a flashlight and go out to the street, the power lines are. Oh, yeah, that might be a bit hard to test those... LOL

Haha, the unstoppable force.

When you say, “possibly a loose connection in the relay box or the wire to terminal 87”, that is the same thing correct? It doesn’t appear there is a main power wire to the relay box, just individual wires to each relay? That might be a ridiculous question but dealing with electrical is by no means my strong suit, I’m more of a break while I’m figuring it out then have to fix it kind of guy, that may be obvious though.

Yep, same thing. GM uses a couple designs, the most common for that time is a buss bar that runs down a central area and the fuses have a tap attached to that. Then when the fuse is installed, the power goes out the other leg of the fuse. Notice in your pictures all the open connectors? Those are unused taps because they use the same block in a few applications. In yours that is open, in an Impala that might be for a power window or ignition feed. It's one reason why fuse boxes are something you cannot memorize. Even in the same make they are different, and in the same model they may change if there is an update or year change. Relay wise they bounce around in those years, so they just used plug in connections and then made up the charts after the design was finished. It's why the second item I go after if it's anything that may be electrical is OE wiring. But even then, you can get tripped up if there was an error. Take the relay in your truck. The trigger side (coil) doesn't care which way the power goes through it. In yours Terminal 86 is grounded using the Black w/white wire and 85 is switched power in the green with white wire. But say that Tom was not paying attention that day and reversed those. It's no big deal in that it still works. However, if you were looking at the schematic and are seeing a 2 second power pulse on the "Ground" terminal and the terminal that is supposed to be the pulsed power is showing as a solid short it can get interesting.

Talking to someone that knows exactly what they’re talking about is the only thing keeping me sane on this project lol, a huge thank you to you. In the morning I’m going to be re-reading most of this, going over my own notes and giving it heck again. One thing I’ve learned is when I get lost, start from the beginning, do it like before you thought you knew what you were talking about lol, that’s my reset. I really appreciate your input.

No rush. I know what you mean. My solution now is a cheap video camera, it watches me while I work, and I'll talk at each stage just like the big YouTube channels. Then if I get called away or running in circles I just go back and look at what I did. So, the video might record "testing pump relay, power to 87 ground on 86 load test on 30 shows pump on, no trigger from ECM on 85" or "oil pressure switch jumped, pump on, circuit ok" Also why I love my latest scan tools as they do live screen recording or screenshots. The older tools only allowed you to print, which worked but is a pain to track info with. Also why I'm so glad that huge screen TVs are cheap, Put a wiring diagram on a 10" screen and you get scroll happy, toss it up on a 60" screen and now you can set in the car and still see it as you hunt for that dark blue wire mixed in with the black and gray wires that have 20 years of dirt and tape residue on them. Plus, when you get cross eyed from that you can toss training or another video up there and take a break.

Preach Brother!

Lol, okay. well, I believe I’m making some progress and I finally found what and where the ground wires were online, and I think it’s possible (mostly since I can barely see one and haven’t found the other yet) that my ground wire to the rear of the cylinder heads might lead me to the promised land. I’m super excited about the fact I can’t see them and hardly get to them with a wrench. What size bolt head (wrench size) am I needing for this and is there any particular way of going about this? I’m trying not to remove the distributor if I don’t have to because I’m not eligible for another up in pay grade for at least a year (joke). Any advice is surely appreciated. Oh, alright, tornado warning just appeared, you know what they say, when it rains, i guess you might get a tornado.

I wish I had both those options, video record everything, which I’m sure I could figure a way but having the big monitor would be awesome and a new, modern higher end scanner would be nice. I only have the cheap version and honestly it does help a bunch.

I've repaired so many of those grounds I lost track. It's normally either a 10 or 11 mm, guess it depends on who grabbed the bolt, a flex head ratcheting wrench is a good thing there. Keep your head down those atmospheric vacuum cleaners can cause problems.

This one on left side facing trans dipstick tube is ever so special to try and get a wrench on, I haven’t located the other yet, it can’t be too far, just behind something.

Do you happen to have an image of the other bolt? because if the land of milk and honey is behind the pic I sent, I’ll never see it.