740T intermittent non-start and more

Reubo · 2025-07-23T06:54:49+00:00

Another day and another issue on the 87’ 740, actually it’s multiple. 1st: getting a lot of condensation on the roof of the boot, can’t see any obvious leak...

Reubo

jamesinc thanks! So when cleaning out #1 do I take that out of the car?

jamesinc

Yeah, there's two 12mm bolts that hold it in, it's a bit fiddly but you can do it without removing the manifold

carnut222

Regarding the condensation in the boot, have a look in the spare tyre well and see if there's any water in there. Also, IIRC there are some drain hoses from the rear parcel shelf area - check to see if they're intact, connected, and routed through the rear floor below the parcel shelf. Also check to see if there's any water collecting or trapped on the pockets outboard of the spare wheel well in front of the tail lamps. Tail lamp gaskets can leak - if there's water in there, it may be tail lamp gasket leaks.

Reubo

carnut222 yea I had a look in the spare wheel spot and there’s none there but there is water collecting (it’s currently raining here) in the two spots either side below the taillights. I can’t figure out where exactly the water is coming in though which is frustrating. It seems to be the taillight gaskets but also maybe in the trim around the taillights

Forg

Do 740’s do what 240’s do, and have the front & rear windscreen seals shrivel & stop sealing properly when the rubber gets old?

Mr Laurence

Hi Reubo. From my own recent Volvo woes I would bet your intermittent non-start is indeed a dicky fuel pump relay as suggested by Ramrod. Its a simple thing to rule out the relay. When the car refuses to start, pull the fuse cover (Im assuming yours has the fusebox by the passenger door hinge area like the 240) and jumper between fuse 4 and fuse 6 right side (from the top). This should force the fuel pump on. If car starts assume relay is intermittent. Swap or reflow solder the relay to fix.

My take on these relays is simple. Assume every original unmolested fuel pump relay to be intermittent or bordering intermittent. In my effort to fix my non-start issue, I acquired a bunch of those evil white relays. Thankyou U-Pullit. Every one was either dicky or reflowed. My car's original relay was truly evil. Under a decent stereo microscope I could not find the culprit broken solder joint, but the meter said sorry its open cct. Reflow solder fixed it. So if yours is an original relay, my suggestion is pull it and either replace with a known good one or open it up and plug in the soldering iron.

I hope I'm right…..good luck Reubo. MK

Reubo

Mr Laurence Thanks for the response! I’ll have to check that out, unfortunately my relays are behind the ash tray in the front dash so a bit harder to access. It’s only happened once where it wouldn’t turn on fully but still worth checking. I’ve never done any soldering but might be time to learn by the sounds of its. Thanks!

Reubo

Mr Laurence Gday Me Laurence it’s been a while but I’m only just getting around to that relay issue, it has been getting worse with not starting.

I tried swapping the relay from my 1988 parts car but that didn’t work either. Open inspecting both the “original” one appears to be a replacement made in 1990 and the one from the 1988 doesn’t look too good either (photographed).

I was just wondering what you meant by jumping fuse 4 and 6 and how I would do that to test my car? I think the fuses may be different also.
Thanks Image description

Mr Laurence

Hi Reubo. Yes, I have to remember the 740 is configured different to the 240, which has the fuel pump relay tucked behind the glove box. I visited Gillman U pullit in Adelaide recently and they had both a 740 and a 1989 240. The differences were obvious inside the car. If you are not a regular solderer consider a cheapie on line fuel pump relay. I say thay gritting my teeth to be honest. My take is the original stuff is best quality, and a quick solder reflow beats an unknown product from China, bless their souls.Google be your friend! MK Good hunting.

ramrod

Reubo

That’s on a 240 (the fuse trick)

What problem are you experiencing?

jamesinc

@Reubo the pic didn't come through

Reubo

ramrod just the same intermittent non start, except a bit more frequent now.

I tried both relays when it wasn’t starting and it still didn’t work

ramrod

What’s missing when you cannot start?

Spark or fuel?

Where abouts is the vehicle?

Reubo

ramrod
I’m pretty sure it’s fuel, I sprayed some “start ya bastard” in the intake last time it wouldn’t start and it started after that

ramrod

Yep.

Are you able to hear the fuel pumps buzzing when the engine is refusing to start?

If so, fuel pressure needs to be tested

Also, you need to verify whether or not the injectors are working. Test with noid lamp

carnut222

How's your radio suppression relay (for the injectors) and its associated connector? This should be located near the coolant bottle on the inner guard. There's an identical relay on the LH side shock tower (IIRC) for the electric fans…you can try swapping. It's a 4-pin relay with round pins. Often the connector's rubber casings around the pin receptacles can degrade, which can lead to excessive corrosion and/or poor contact.

ramrod

Very very common problem on 740.

Mr Laurence

Hello Mr Reubo! I am still alive and my volvo Mr Laurence wishes your 740 a speedy recovery lol. Pardon the delay. Your relay photo shows a resoldered relay. So it's had issues previously. No harm in attacking it with the soldering iron. Redo every joint. Do your spare relay too. If the problem persists you need a second pair of ears under the car to listen for fuel pump joy or misery.

Good luck.

jamesinc

@Mr Laurence did you mean to post this somewhere else?