Cranks but won't start

[Mooseman]

'05+ have the filter on the pump.

 

[coolride]

I've seen pictures of pumps with filters that hang off the bottom, and also filters inside the pump assembly "cans." By "can" I mean that plastic canister that holds gas when the pump is removed.

 

[Mooseman]

I think those are the old type with the sock on the bottom. The newer ones have the filter inside that canister.

 

[coolride]

I think those are the old type with the sock on the bottom. The newer ones have the filter inside that canister.

I pulled the pump and see a filter inside the canister.

When I pulled the pump I noticed the O-ring was inside the tank (wrapped around the body of the pump assembly.) I don't know if the O-ring fell during pump installation, or during removal.

I attempted to reinstall the pump with the O-ring in place and now the lock ring won't engage the tabs. Is this a common problem?

It's a Bosch pump with a green O-ring.

 

[coolride]

Here's a look at the tank flange. It's just tank material (apparently some type of laminate.) There's no "sleeve" type OEM O-ring.

 

[Mooseman]

There should be a channel all around for the o-ring to sit in. Check inside the tank for a piece of plastic or metal that may have fallen in.

 

[coolride]

Yeah, there's a channel for the o-ring. The problem is, the o-ring is so thick that I can't get the lock ring started.

Next attempt I'll lube the o-ring with silicone grease. Maybe that will help it to spread and flatten out enough to get the lock ring down.

 

[NJTB]

That happend to me, too. Wound up buying the J tool (sorry, don't remember the PN) and installed it that way. I do remember there's about 3 for the TB, look it up for your year.

 

[coolride]

Testing the fuel pump harness. With the key on I'm getting 4.9 volts between the grey and the green. Is this correct?

 

[Mooseman]

Is that for the fuel pump? It should have 4 wires. That's probably for the tank pressure sensor. In that case, you should have 5v between black (-) and gray (5v ref). Green is the sensor output.

On the pump plug, it's:
Gray: 12v+
Blk: ground
ppl and orn/blk: level sender output

 

[coolride]

Thank you. Just tested again.

I see 12v when key is on but it quickly backs off to zero. So temporarily,,,there is 12V. During cranking I see 10V.

 

[coolride]

Ran test again, but used a lead to the neg. battery terminal for the ground (reliable ground.)

Same results. Saw battery voltage with the key on, but only momentarily, then voltage dropped to zero.

While cranking it had 10V.

 

[Mooseman]

That is normal. When in RUN, the PCM primes the pump for just a couple of seconds and switches off the relay until you turn the key to START and stays running. Instead on a meter, use something that draws some amps, like a headlight bulb, to see if enough amps go through the wiring. It can happen that you can see a no load voltage but drops off with an actual load. When plugged in, do you hear the pump run while it's priming?

That's pretty low voltage while cranking. Is the battery good?

 

[coolride]

The battery has been sitting for a looong time. So it's a little weak. I'll get it onto a charger tonight. The pump is out of the tank and in a different room but back when it was installed yes, I could hear it prime.

If there's low amps under load, what's the busted component?

 

[Mooseman]

Could be the relay, wiring, connector or fuse contact. They've been known to get loose and/or corrode.

 

[coolride]

I tested both fuel level sensors. The new one (background) is whacked. The ohm readings are all over the place. No wonder my fuel gauge wasn't working right. The old one works fine.

 

[coolride]

Looking at the Bosch paper work now, and wondering how to get a refund from Amazon. I want a better pump. Called Newparts Inc. of Gordonsville, TN (the seller) and left a voicemail. Was told to expect an email reply.

 

[coolride]

For load testing the circuit, I have a bulb wired up as the load. I can do a high beam test, and a low beam test. (now what?)

 

[coolride]

Does the load test have to be done with the pump installed? The problem I'm seeing is that the PCM cuts power to the pump after a moment with the key on. Hard to test like that.

 

[Mooseman]

Unfortunately, that's how the PCM works. What you could do is pull the starter relay and turn the key to CRANK. It will command the fuel pump on while cranking.

 

[coolride]

Thanks. I'm getting. One step at a time.

 

[coolride]

Rigged up a load with the stuff I could find (nails, alligator clips, wire, and scrap wood.) It works, but doesn't look great. This is a low beam load.

 

[coolride]

Load testing completed. I am reading 0.1v negative side and 0.3v positive side. So no problems are obvious. I'm thinking next; get the pump installed and hook up the tank. I'll repeat the load test with the tank connected, but not strapped up.

 

[coolride]

Spoke to Bosch:

Don't buy a Bosch fuel pump (or anything) from a non-approved Online Partner.

 

[NJTB]

@coolride
Amazing, isn't it. Back in the day, GM had a problem with distributor caps. They were scrapping defective ones, but they kept turning up, then were returned to the store again.
Turns out someone was pulling the caps out of the trash and re selling them.

 

[coolride]

Just ordered ACDelco part ##MU1655 w/seal. After tax and shipping, $305.

Bosch said they'll give me a refund if I send them the old pump and a copy of the invoice for the new one.

 

[coolride]

Pump is delivered. I'm surprised that ACDelco sent a green o-ring, and not that black, collar like, seal. Isn't the collared seal OEM?




The tank is almost half full. I'm headed out now to buy another gas can. That small transfer pump has been very useful. Picked it up at WalMart for less than 10 bucks.

 

[Mooseman]

There could have been a design change preventing the use of the old style seal. I don't think it really matters as long as it seals.

 

[Reprise]

I should've been following this thread sooner...

Had the same issue with my new pump (different make; HP vs stock flow) -- took forever for fuel level to update on both the gauge & DIC. Vendor sent me a new pump module (and didn't ask for the old one back).

Comparing the 'new new' one, vs the first new one... yep... you could feel the difference in the two mechanisms. The first one was definitely sticking a bit, compared to the second one.

So... you're not the only one with 'sending unit blues'.

Re: the seal. I did get the 'collared' seal, vs. the green o-ring. And it was (just as -?) hard to get the (new) ring locked in. I've seen some people mentioning that pulling the lock tabs on the tank upward a bit can help. Maybe a Dremel to the underside would help, too? Or some sandpaper, even? It's definitely one of the worst parts of the job, although secondary to getting the old corroded one off.

Looking at the amount of material on the collared vs. the o-ring... I think that's why GM revised the seal, myself -- cost of the part. Seems that the companies that use the o-ring... it's always green. So, a chance of one global supplier in the chain -?

I also used a transfer pump to remove fuel from the tank. That type never worked well for me, so I picked up a battery-powered one on special from HF... I think I paid $8 or so, on sale awhile back. Was able to pump into a 5gal can, and then put the gas back in the tank after job finished. Really works a treat.

 

[coolride]

Pumped 8 gallons out of the tank then gave the inside a good clean.

Lubed the o-ring with silicone grease and laid her in the groove. Then carefully dropped the pump into place.



Illustrated using the old lock ring: I tapped down the lead-in edge, and also lightly ran a file over the top so the edge wasn't square. (It's not always easy getting these rings started.)



Buttered up everything with anti-seize (for rust prevention) and the ring spun into position with no issues.

 

[coolride]

The tank was lifted into position and the straps were bolted up tight. This TB has not been off jack stands since last September.

Feels good the see her on the ground.


Added 6 gallons and turned the key. The engine fired right up and I backed her outside. Used the TB to visit my parents today. So far everything is good.


Time to clean this garage.

 

[coolride]

I'm about to check the fuel pump relay and it's wiring. This morning I plan to jump 87 and 30 and then listen for the pump to engage.

Question: Does the relay supply power to the pump all the time during operation? Or does it switch on and off depending on fuel demand?

The reason I ask is, I'm wondering If I can drive around normally with the relay jumped?

I've logged every start attempt. 14 starts, a non-start, then a start, and another non-start.

 

[budwich]

are you NOW saying "NO-crank, no start" or "crank, no-start"?

 

[TJBaker57]

I agree with @budwich . We need copious details of the current status!!

I'm about to check the starter relay and it's wiring. This morning I plan to jump 87 and 30 and then listen for the pump to engage.

Ummm, do what now?? This speaks of two diffefent components/systems. Checking starter relay implies you have a no crank,,,, but then you speak of listening for the pump?? That suggests a crank-no-start. Makes it unclear what is going on here.

Question: Does the relay supply power to the pump all the time during operation?

F/P relay energized whenever engine is running, yes. (Unless there is a security issue and PCM hasn't got the fuel continue OK from the BCM, but that's another story)

 

[coolride]

are you NOW saying "NO-crank, no start" or "crank, no-start"?

That's my fault. I made a mistake and typed "starter relay" where I should have typed "fuel pump relay." It's Crank, No Start.

 

[budwich]

OK... so in essence, you have done nothing... except you have a newer overall "age of the truck" as it has improved. So... you don't have to keep trying to start the thing which will only cause your starter to burn out. All you need to do is remove the fuel relay, connect your meter up to the socket area which has the connection that goes to the pcm (ie. the control wire).... set it on dc volts. Turn the key to on and watch your meter. Turn the key to off and repeat. You should always see a 12v "blip" for every key action. This is a check for the circuitry back towards the control system and has nothing to do with your physical pump. Once, you have got significant success test, based on your "sheet", more than 20, you can go from the results there after.

Further alternative there after is to either pinprobe the wire going to the fuel pump or "hang the relay is "free air" so that you can get access to the connection (much like your "frankenstein" light bulb test) and repeating the same test again. You should see the same results.

 

[coolride]

I know terminals 87 and 30. This picture is from a YT video. I find battery voltage all the time at the lower right terminal (where the line is drawn.) (Left of 20amp fuse.)

 

[coolride]

And to the left of that, I see battery voltage at the ground terminal.

Now things get complicated...

 

[TJBaker57]

Give me a few moments.... might have some insights gleaned from bench testing here

 

[coolride]

OK... so in essence, you have done nothing... except you have a newer overall "age of the truck" as it has improved. So... you don't have to keep trying to start the thing which will only cause your starter to burn out. All you need to do is remove the fuel relay, connect your meter up to the socket area which has the connection that goes to the pcm (ie. the control wire).... set it on dc volts. Turn the key to on and watch your meter. Turn the key to off and repeat. You should always see a 12v "blip" for every key action. This is a check for the circuitry back towards the control system and has nothing to do with your physical pump. Once, you have got significant success test, based on your "sheet", more than 20, you can go from the results there after.

Further alternative there after is to either pinprobe the wire going to the fuel pump or "hang the relay is "free air" so that you can get access to the connection (much like your "frankenstein" light bulb test) and repeating the same test again. You should see the same results.

Is this what you mean budwich?

I put the meter on the upper right terminal; I do see battery voltage when the key is turned to on. (Left of 10amp fuse.)