Hey there,

New to the forum. I've got a Volvo 740 non-turbo, wagon, 1986, which I have slowly been restoring/fixing!

Each time I work through the gremlins (mainly electrical) a new problem arises. This time the engine keeps dying on me. I thought this was the coolant temp sensor to the injectors but I recently replaced that along with the O2 sensor and the thermostat.

After these replacements, the car ran for a while and then died on me after a couple of days. I swapped the fuel pump relay out for a new one and it fired back up with no problem. Then I tried putting it in reverse and the engine died. It fired back up and ran for about 20mins before cutting out. I noticed the fuel pump relay was really warm, so I let it cool down. After it cooled down it fired back up again. I drove the car around the block and it seemed to do well but after 10mins it died and would turn over again. I swapped out the new relay for an older one and it fired back up. I drove it for 30seconds before it died again. I limped it home on the old relay.

Now the car won't start on the new relay, on the old relay the engine cuts out after 5mins. I've heard that the overheating fuel pump relay can come from a bad pump. A Volvo specialist had just replaced the fuel filter for me and tested the pump under the driver's side front door. They said it was fine. I tested the volts going to the pump with the engine on and I was reading 12.6-13v. I can hear the in-tank fuel pump prime itself ok but I think I might be smelling gas from it.

Sorry for the long-winded backstory but there is lots of similar info out there but nothing the same as this! I'm thinking it's dad fuel pump/pumps! Wiring harness issues, ECU issues, in proper grounding?

If anyone has had this problem - with this year of 740 - or knows how to eliminate certain items, that would be really helpful.

Cheers,
Mike

WHAT I"VE REPLACED/FIXED SO FAR:

New leads
New plugs
New Air filter
New Oil filter
New Fuel Filter
New fuel line to the manifold
New Fuel regulator (36psi)
New coolant temp sensor
New Thermostate
New O2 Sensor
New Flame Trap
Cleaned injectors with new O rings.
Cleaned the MAF Sensor with MAF Cleaner.
New resonator and muffler
Reground all grounds under the hood.
Fixed all-electric windows
Fixed all the brake lights.

 

I think you are on the right track that if the FPR is getting hot, the fuel pump is drawing too much current and on its way out. Check out Youtube for any vids like:


You may want to test to see how much current is going through the relay. Google to see if you can find a spec on the normal current draw for the pump. I suspect when the tech tested it, they checked fuel pressure not current draw. I saw an old post that suggested the external pump should draw less than 9A (7.5A as the norm) and the in-tank pump was something like 1.5A - but not sure if that source is accurate.

Also, here's a good read:

https://www.volvoclub.org.uk/faq/FuelSystem.html

 

Whatever it is, it is not your engine dying! You got some fuel delivery issue pump/relay etc. Hopefully all the parts you swapped are good quality.