740 GLE Won't Start When Hot - Wait 1/2 Hour Okay
740 GLE Won't Start When Hot - Wait 1/2 Hour Okay
740 GLE Won't Start When Hot - Wait 1/2 Hour Okay. I'm having this problem with my '90 740 Wagon. Very frustrating - have replaced fuel pump relay, fuel pump, fly-wheel sensor... all to no avail. No error codes from computer are showing up. Any ideas please?????????
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wojeepster
- Posts: 259
- Joined: 15 November 2005
- Year and Model:
- Location: Hendersonville, NC
Try the ignition module on the drivers fender. Before you go and replace it get a can of that freeze spray. When car quits you can give it a shot and it should start working again. If it doesnt your problem lies elsewhere.
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Kmaniac in California USA
- Posts: 301
- Joined: 15 January 2005
- Year and Model:
- Location: Concord, California USA
- Been thanked: 1 time
I had a similar problem with my 740. I found the cause to be a fuel pick up filter sock (in the tank) that had deteriorated, causing dirt to enter both fuel pumps, causing both pumps to fail. The dirt contamination in the main fuel pump caused it to run intermitently, leaving me stranded when the car was warm and starting flawlessly again when it cooled off. Search this forum for my screne name and you can read about my adventures with the fuel pumps.
Now your car has two fuel pumps. Which one did you replace? The in-tank fuel pump is, well, in the fuel tank. It has a filter sock on the pick up end. The other pump, the main pump, is under the car below the driver's seat. The main fuel filter is down stream of the main fuel pump.
Anyway, read my old posts and let me know if you have any questions.
Now your car has two fuel pumps. Which one did you replace? The in-tank fuel pump is, well, in the fuel tank. It has a filter sock on the pick up end. The other pump, the main pump, is under the car below the driver's seat. The main fuel filter is down stream of the main fuel pump.
Anyway, read my old posts and let me know if you have any questions.
Chris the "K MANIAC"
1986 740 GLE
(5) 1964 Chrysler 300-K's
1986 740 GLE
(5) 1964 Chrysler 300-K's
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Kmaniac in California USA
- Posts: 301
- Joined: 15 January 2005
- Year and Model:
- Location: Concord, California USA
- Been thanked: 1 time
So, you changed the main fuel pump without changing or even looking at the in-tank pump. I was hoping that wasn't the case.
One should not change the main fuel pump in a Volvo without changing, or at least visually inspecting the in-tank pump and filter sock at the same time. The fuel pick-up filter sock with detierioate over time. This filter is designed to protect both fuel pumps from dirt contamination that will destroy them both. If you have any size hole in the pick up filter, dirt will destroy the new main fuel pump in very short order. I have read at least one post in this forum from someone who had a private mechanic replace the main fuel pump in his 740 three times, every 30 days, and couldn't figure out why his new pumps were always defective. He had no clue there was a pump and filter in the tank.
One other thing you should know. Even though the car has two fuel pumps that work together, the car will appear to run normally with just the main fuel pump working by itself. However, it will not run at all if the main pump ceases to function and the in-tank pump continues to run. It is common for your in-tank pump to fail without knowing it.
Immediately check your fuse box and look at the fuse for the in-tank pump. It is fuse 11 in my 1986 740 (the main fuel pump uses fuse 1). If it is blown, then your in-tank pump is toasted. Even if this fuse is good, I suggest pulling the in-tank pump and sender unit assembly from your gas tank and visually look at the filter sock. If you find any holes in it, then in-tank pump and filter replacement are mandatory. Then be prepared to replace the main fuel pump again, because you will have caused irreparable damage to it. Even if the in-tank filter seems to look good, you may as well replace it and the in-tank pump anyway, since you have it out.
This is an easy job for the DIY'er. Be sure your fuel level is below 1/2 tank before you start. There is a hatch cover on the trunk floor between the rear wheels, which you remove to gain access to the tank sender unit assembly without crawling under the car. Disconnect the fuel hoses, disconnect the wiring inside the trunk (don't try to pull them off the sender unit), unscrew the retaining ring and the unit will pull straight out throught the hatch. Installation is the reverse.
Good luck with this and let us know what you find.
One should not change the main fuel pump in a Volvo without changing, or at least visually inspecting the in-tank pump and filter sock at the same time. The fuel pick-up filter sock with detierioate over time. This filter is designed to protect both fuel pumps from dirt contamination that will destroy them both. If you have any size hole in the pick up filter, dirt will destroy the new main fuel pump in very short order. I have read at least one post in this forum from someone who had a private mechanic replace the main fuel pump in his 740 three times, every 30 days, and couldn't figure out why his new pumps were always defective. He had no clue there was a pump and filter in the tank.
One other thing you should know. Even though the car has two fuel pumps that work together, the car will appear to run normally with just the main fuel pump working by itself. However, it will not run at all if the main pump ceases to function and the in-tank pump continues to run. It is common for your in-tank pump to fail without knowing it.
Immediately check your fuse box and look at the fuse for the in-tank pump. It is fuse 11 in my 1986 740 (the main fuel pump uses fuse 1). If it is blown, then your in-tank pump is toasted. Even if this fuse is good, I suggest pulling the in-tank pump and sender unit assembly from your gas tank and visually look at the filter sock. If you find any holes in it, then in-tank pump and filter replacement are mandatory. Then be prepared to replace the main fuel pump again, because you will have caused irreparable damage to it. Even if the in-tank filter seems to look good, you may as well replace it and the in-tank pump anyway, since you have it out.
This is an easy job for the DIY'er. Be sure your fuel level is below 1/2 tank before you start. There is a hatch cover on the trunk floor between the rear wheels, which you remove to gain access to the tank sender unit assembly without crawling under the car. Disconnect the fuel hoses, disconnect the wiring inside the trunk (don't try to pull them off the sender unit), unscrew the retaining ring and the unit will pull straight out throught the hatch. Installation is the reverse.
Good luck with this and let us know what you find.
Chris the "K MANIAC"
1986 740 GLE
(5) 1964 Chrysler 300-K's
1986 740 GLE
(5) 1964 Chrysler 300-K's
I have found the problem - hurray! I found the fix on the UK Volvo Club site - the problem was the noise suppression relay, which also supplies + power to the fuel injectors. There are two identical relays side by side - the noise suppression and the auxiliary fan relays. After reading the following diagnosis for the ns relay, I switched them and the car started right away. Switched them back and no start. Back again and started again right away!
Problem diagnosis: When this relay fails, it can cause:
Problem diagnosis: When this relay fails, it can cause:
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Kmaniac in California USA
- Posts: 301
- Joined: 15 January 2005
- Year and Model:
- Location: Concord, California USA
- Been thanked: 1 time
Way to Go!! I love to hear success stories! 
Chris the "K MANIAC"
1986 740 GLE
(5) 1964 Chrysler 300-K's
1986 740 GLE
(5) 1964 Chrysler 300-K's
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wojeepster
- Posts: 259
- Joined: 15 November 2005
- Year and Model:
- Location: Hendersonville, NC
Thanks you just added to my won't start when hot list!
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