07 Rendezvous Crank no start

[TimeTravel]

Waiting for the tow truck. 😭

 

[TimeTravel]

I'm home. I've dropped the tank and am testing power directly at the pump plug. I have 12.5 volts on the gray wire, a resistance of about 1280 on the purple wire and I have ground to the black/white wire and black wire.

 

[TollKeeper]

I wouldnt order anything yet.. Verify the problem first.

I know RA is cheaper, and I even have a discount code for them. But warrantys can be a pain, and returns.

If I am going new, I try to go local just for those 2 reasons.... Unless I am just flipping the car.

Thats why I said this....

So your headed in the right direction. Unfortunately, I cant help much further than this. It could be a relay, PCM, BCM, or??

Electrical is not my fortay.

 

[TimeTravel]

Thats why I said this....

So your headed in the right direction. Unfortunately, I cant help much further than this. It could be a relay, PCM, BCM, or??

Electrical is not my fortay.

Thats why I said this....

So your headed in the right direction. Unfortunately, I cant help much further than this. It could be a relay, PCM, BCM, or??

Electrical is not my fortay.

The pump gets power when I jump the relay. It should pump. When I remove the relay jumper there is no longer power, I checked. There are only four wires. A big gray and a big black. These are pump power and pump ground. And then there are a little black/white and purple. The purple and black/white wire is the resistance and ground wire for the gauge.

I'm not sure what else there is 🤔

Does anyone else have any advice. I'm going to call and see if there's a replacement available and put it in. I'll let y'all know if it does anything.

 

[TollKeeper]

Swap the relay for another one in the fuse panel. They are cheap, and it may have failed internally. They are pretty cheap to buy as well..

Also, you never told me about your dash, when the truck is in a no start condition. What all lights do you have on..

Does one of them say Security? It may be in that small multi-display panel.

Looks like this...

 

[TimeTravel]

I've never seen that security light before. On my car you can tell if the key is disabling the security when the small red light to the right of the instrument panel will flash until the key is inserted.

There is no fuel pump in the car at the moment.

 

[TimeTravel]

This is definitely not a security problem. It tries to start with starting fluid and the pump has power for a few seconds when the key is turned to the on position. The pump also gets power when the relay is bypassed. I'm pretty sure this is a shitty pump design that overheats during a heatwave and hard use. They didn't have a replacement pump for me locally but it should be here Monday.

 

[TollKeeper]

Either that, or the BCM gremlin has bit. These were known to have bad BCM modules. I had to replace 2 of them in the span of owning my truck.

 

[TimeTravel]

I don't have a wire diagram but I'm assuming that you mean the BCM sends low voltage signal to the fuel pump relay which powers the fuel pump. My relay is getting power and I don't have any voltage drop at the fuel pump. I'm not sure and what other way the BCM could affect a fuel pump.

When I've read there's a few major things that can cause repeated fuel pump failure.

Number one is contaminated fuel and debris in the fuel tank. Maybe this happened the first time but I've cleaned the fuel tank twice now so I don't think this is likely.

Number two I got a bad connection somewhere that is causing resistance in the pump voltage for ground wire that is over amping the pump. I've replaced the relay and all the wire connections that I found in the circuit looked shiny and clean. Also I'm not getting any voltage drop compared to testing directly from the battery 12.5 volts and directly at the plug that plugs into the pump. Although I won't rule this out and will continue examining the wires for bad connection.

Number three fuel pump regulator is sticking too high of a pressure and overworking the pump causing it to overheat. Every time I've tested my fuel pressure it's been about 60 PSI with the car off and 58 PSI with the car running. If someone could verify if this is a good range that would be very helpful. Although I believe it is and I think I can rule out the fuel regulator.

Number four low fuel level in the gas tank overheating the pump. This might be the case or maybe just a contributing factor. When I drain the fuel I only had about 5 gallons left in a tank.

Number five the engine is getting hot and it's also really hot outside. I've been running Amazon flex deliveries so I've been running the car stop and go for 3 to 4 hours at a time. The fuel in the fuel return line might be getting really hot and overheating the fuel pump. It's been consistently in the 90s here if not hotter and I've done regular runs from 2:00 p.m. to 6:00 p.m. during the hottest times of the day.

 

[TimeTravel]

I'm tempted to run new power and ground wires directly from the battery with my own relay and fuse just to be sure I don't have an overampage problem. Does anyone know what amperage these pumps should be running? The circuit has a 15amp fuse. Maybe I should put a 10 amp or even smaller in there to make sure the fuse blows before the pump overworks itself.

 

[TimeTravel]

Also I suppose I could try adding a fuel return cooler.

 

[TollKeeper]

In my humble opinion... The problem has not been found. I think doing all/any that is overboard.

Need to definitively find the problem at hand, and then find the course of action.

What you do know is that power is getting to the relay, but the command to switch the relay is not happening?

If you bypass the relay, the system pressurizes, and the car starts?

So the command to the relay is where the focus needs to be.
What conditions have to be met for this to occur, I dont know.

 

[TollKeeper]

It takes a bit of work. but some good info given in this thread.

https://www.justanswer.com/buick/dv5o9-buick-rendezvous-3-5-activates-fuel-pump-relay.html

Minimize the chat window
Click the "See More" box

 

[TimeTravel]

In my humble opinion... The problem has not been found. I think doing all/any that is overboard.

Need to definitively find the problem at hand, and then find the course of action.

What you do know is that power is getting to the relay, but the command to switch the relay is not happening?

If you bypass the relay, the system pressurizes, and the car starts?

So the command to the relay is where the focus needs to be.
What conditions have to be met for this to occur, I dont know.

No. As I said, the relay is working properly. I have power at the fuel pump. The fuel pump is not running when it has power. The fuel pump is bad.

 

[TollKeeper]

2 fuel pumps doing the same thing, in a very short amount of time? I would be looking at that harness from the pump to the C305 Connector

Jump the relay so that it should be running constant. Grab that harness, and listen. See if you can hear it powering on, off, etc.

 

[TimeTravel]

I don't need to jiggle the wire harness to make sure I have power at the pump. I have a meter with DC voltage and continuity setting. I've checked them both a dozen times. The pump has power directly at the pump.

I repeat the pump has power directly at the pump. As shown in the above picture where the red arrows are pointed.

 

[TimeTravel]

I suppose an argument could be made if the connector is bad it's not actually getting power from that last plug to the fuel pump so I took off the cap and took a look at the connections directly.
They are shiny. If I had a bad connection I'd be very surprised because if I did have a bad connection I had expected to see discoloration. Especially a bad enough connection to overamp a pump

 

[TimeTravel]

To triple check the continuity from the c305 to the actual inside of the first fuel pump.
From the c305 to the power wire and this picture. Continuity shown on the meter.

From pump ground to pump ground again from c305 connection to the inside of the pump. Good continuity as shown on the meter.

 

[TimeTravel]

And I know y'all might be asking where's the actual pump to that pump. The answer is I'm just using this old broken one as a cover so I don't get dirt in my fuel tank while I'm waiting for my fuel pump to arrive at AutoZone.

 

[TimeTravel]

If there is an issue in the wiring on my vehicle it's an intermittent bad connection that's over amping the pump. It's not something that would be keeping a good pump from running.