1987 Silverado fuel issue

[Rusty Nail]

I have put my fuel supply issue on hold while travelling for work. However, I believe I determined that I'm not getting any power to the fuel pump relay when I turn on the key. Not sure what could explain that, given that no code was shown which would seem to explain it. I also jumped 12v directly from the battery to the relay connector lead which, I think, is supposed to energize the pump as a test point. Still nothing from the pump. Any ideas are welcome.

Yep. That plug turns on the fuel pump when connected to the battery. If it didn't it's likely time for a new pump.
I only recommend GM or Airtex for gmt400. I installed GM in my Blazer @ $35 bucks AND about 5 inches of fuel line. You'll see.
Make damned sure to install the new ground wire provided with the pump.
Mmmkay?

Good luck.

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[hamm]

KnuckleBuster, when you say " disconnect the pump connector and check for power and ground", which connector do you mean? Then on to the pump relay? The one at the tank?

I put 12V to the lead at the relay connector which I believe should have started the pump, but I didn't hear anything. Not positive I had the correct contact to try there.

 

[hamm]

Rusty nail... The pump in there now is a Delphi and has less than 500 miles on it. I find it hard to believe that it's gone bad already. When this happened before, and I dropped the tank and replaced the pump, the system started working again, but I have the old pump and it DOES WORK. I have no idea why the system stopped working before, when the pump was good, or why it started working after switching one good pump out for another good pump. This time, the symptoms are the same - Sudden no-worky. I hesitate to drop the tank again, but I will if I have to. I just want to look into other reasons why the system stopped working, since the previously replaced pump seems to have not been the actual problem.

 

[Rickf]

Any sign of non-rent paying rodent tenants eating lunch along the harness?

 

[hamm]

Any sign of non-rent paying rodent tenants eating lunch along the harness?

No. Haven't seen any sign of them.

 

[KnuckleBuster]

KnuckleBuster, when you say " disconnect the pump connector and check for power and ground", which connector do you mean? Then on to the pump relay? The one at the tank?

I put 12V to the lead at the relay connector which I believe should have started the pump, but I didn't hear anything. Not positive I had the correct contact to try there.

The connector for the tank unit. It should be accessible through the LR wheel well. The connector and the ground are attached to the top of the frame rail. Check the terminals and make sure they still fit snugly.

I usually jump at the relay. Just disconnect it, make sure the B+ is hot, and jump it directly into the pump circuit. Or, use a fused jumper wire attached to the battery to do the same thing.

One thing I forgot to mention: if the pump isn't running with 12v jumped into it, slap the underside of the tank right where the pump sits. Most of the time a failed pump will come back to life. Temporarily, of course.

 

[Ricko1966]

The connector for the tank unit. It should be accessible through the LR wheel well. The connector and the ground are attached to the top of the frame rail. Check the terminals and make sure they still fit snugly.

I usually jump at the relay. Just disconnect it, make sure the B+ is hot, and jump it directly into the pump circuit. Or, use a fused jumper wire attached to the battery to do the same thing.

One thing I forgot to mention: if the pump isn't running with 12v jumped into it, slap the underside of the tank right where the pump sits. Most of the time a failed pump will come back to life. Temporarily, of course.

Was actually taught not to smack the tank to bring a pump back, I still might do it though,depends on where evryone is at the time.The reasoning was. If I smack the tank and the car runs the customer will want to take the car and bring it back,at a more convienent time,or when they have more money,or their dad can fix it,whatever. But when It dies again it will end up at whatever shop is closest when it dies.

 

[KnuckleBuster]

Was actually taught not to smack the tank to bring a pump back, I still might do it though,depends on where evryone is at the time.The reasoning was. If I smack the tank and the car runs the customer will want to take the car and bring it back,at a more convienent time,or when they have more money,or their dad can fix it,whatever. But when It dies again it will end up at whatever shop is closest when it dies.

They might go away (their option, of course), but I doubt most would. But how often is a customer standing there when you're diagnosing a no-start? The vehicle almost always comes in on a hook and then waits its turn in the parking lot, which is likely hours or maybe even a day or so. And even if they are standing there, most won't want to take a chance when you tell them it will likely quit again soon and they'll have too pay for another tow. I remember towing when it was $30. No idea what it is now but it must be around $300. or so. That by itself would keep most people from taking the chance.

 

[Ricko1966]

They might go away (their option, of course), but I doubt most would. But how often is a customer standing there when you're diagnosing a no-start? The vehicle almost always comes in on a hook and then waits its turn in the parking lot, which is likely hours or maybe even a day or so. And even if they are standing there, most won't want to take a chance when you tell them it will likely quit again soon and they'll have too pay for another tow. I remember towing when it was $30. Know idea what it is now but it must be around $300. or so. That by itself would keep most people from taking the chance.

I'll see if I can find my boss from 20+ years ago and let him know. Thanks

 

[KnuckleBuster]

I detect a note of sarcasm there, Ricko1966. Lol. Believe this: If I were losing fuel pump sales because I slapped tanks to get them running, I most certainly would not have been doing it. Have a fun day!

 

[Ricko1966]

@KnuckleBuster I don't have a problem whacking a gas tank with a rubber mallet. And I certainly don't care if you do it,I was also told to quit lighting the tires before I roll in a patch. I've been told lots of things. Things also vary depending on where you are working,the neighborhood you are in,and the income of your customers. I've worked in automotive as a career not a hobby over 40 years,dealerships,independants,big box,high dollar,and low budget ,I've seen lots of things no one would believe. I've actually had someone come to the shop once ramming their P O S truck with tires tied to the front ram their other P.O.S in the rear let it coast ram it again to get it to the shop,people using a garden hose to tow with. I've lifted cars that when the rack went up the tires stayed on the ground,because the shocks and struts were no longer one piece. After diag one time I had a man ask,Is that something I can fix myself. So he didn't know what was wrong but now that he did he thought you tube could fix it for him,he didn't leave his car. I do believe that whacking a gas tank as a diagnoses has several unforseen,unknown effects in the long-term. But I still don't care if you do it. And I still may sometimes ,just depends on the situation.
Have a great day.

 

[bucket]

Was actually taught not to smack the tank to bring a pump back, I still might do it though,depends on where evryone is at the time.The reasoning was. If I smack the tank and the car runs the customer will want to take the car and bring it back,at a more convienent time,or when they have more money,or their dad can fix it,whatever. But when It dies again it will end up at whatever shop is closest when it dies.

Many times over the years, I've tried smacking the tank and maybe just once or twice it has kicked the pump on. I must be unlucky, lol.

If it ever happened on a customer vehicle, I'm sure we didn't tell them, just told them they needed a new fuel pump.

 

[Ricko1966]

@bucket my expierience has been just smacking the tank doesn't do it,,smack the tank while the pump has power. I didn't invent the don't smack the tank policy was just told not to do it anymore. Just like when Firestone told me to quit test driving customer cars. They pay my check I play the game by their rules. These rules change from shop to shop. I'm sure that somebody smacked a tank in front of a customer and cost someone a sale. Firestone told me test drives were not necessary and quit doing it,they asked for an alignment,no need to verify a problem,put it on the rack and align it. Don't drive it afterwards if it's all green it's aligned.Do the next job. The shop I came from before we test drove everything,even before an oil change. We worked the wipers honked the horn used the turn signals listen for ball joints,wheel brgs,then bring it in the shop. I prefer the latter,some people don't even know when they have a developing problem,or forgot their horn doesn't work etc.

 

[Ricko1966]

@bucket I was adding to while you were liking,so hope it's still good.

 

[hamm]

I remember towing when it was $30. No idea what it is now but it must be around $300. or so. That by itself would keep most people from taking the chance.

I was here in town when my rig quit. Maybe 2 miles from my house. It was $85 to bring it home. I have State Farm towing coverage, though.