Hello! New to the forum, a friend gave me this 740 that was in her garage for 15 years Score! have wanted a volvo wagon for a long time. seems to be intact just won't start unless primed. Not getting fuel the main pump will run with a jumper wire the relay clicks when I turn the key and again when I turn to start but the pump will not come on. I pulled the main pump fuse and herd nothing at the gas tank. pulled the fuel line at the fuel rail ant the main pump pushed about a cup of fuel out then just gurgled. I am so excited to get this thing on the road and it seems so close. any help you can give will be great. dose the in tank pump run when the main pump fuse is pulled with a jumper at the relay.

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both pumps run together when the engine turns over, and stop a second after the engine stops turning over. it detects the engine is turning over when the ECU gets timing pulses from the hall sensor in the distributor via the ICU.

on SOME cars, mostly later ones, the pumps run about 1 second when you first turn the key on then stop again.

 

It wants to start but won't. will run when fuel poured into throttle body. without just chug chug sputter stop. ran before sitting for a long time,

 

I'd disconnect the fuel line where it connects to the injector rail, and run a hose from it into a gas-safe container, then crank the car and verify a strong stream of clean gas comes out while its cranking.

any car that sat for 15 years has crud in its tank and system, you need to flush it out and fill it with fresh clean gas.

also, brakes, coolant, hoses, every thing else liquid or rubber should be replaced.

 

It seemed to be empty when I started I have put 9 or 10 gal of fresh fuel ran some about two or three cups out at the fuel rail. thank you for the response! just put new spark plugs. most of my experience has been with carbs.

 

oh, if the fuel pump is running, but there's no power at the injectors, check the 'radio suppression relay' ... this is under the hood on the left (driver) fender... its only on 740/940's, and it provides the power to the fuel injectors.

if you unplug an injector, and switch the ignition on, one of the two pins in the harness plug that goes onto the injector should be a solid 12V (battery voltage). the other pin will be 'floating' and might read 9v or so. with the ignition off, the one thats solid 12V should go to 0V. if you don't see that 12V, find and test the 'radio suppression' relay



'radio suppression'. on 240s, the fuel injection relay was over behind the glove box. on the 740/940 they moved all the relays to a central panel behind the ashtray which put it directly under the radio. the electrical noise from the injectors current pulses caused radio static, so they added another relay under the hood to power the injectors right off the battery, so these heavy current pulses wouldn't be near the radio, hence 'radio (interference) suppression relay'. it otherwise has nothing to do with the radio, and is just the power source for the fuel injectors.

 

That sounds like the next step. thanks for the info I really am getting pumped to start driving my brick. It might be the weekend before I can get back to it.

 

as far as fuel goes I first put 4 or 5 gallons in and then did all the diagnosis, no fuel at the rail added another 5 or 6 gallons in case the in tank pump was not working. poof or rather squirt there was fuel ran it for a while into a container. so I may still have to replace the in tank pump in a side note th gas gauge dose not work.

 

I have a 85 740gle they said that in 86 is when they moved it under the hood are they in a 85 controlled though the fuel pump relay?

 

checked no power to injecters

 

i have no wiring diagrams for 740's before 1991, sorry.

 

thanks for trying can you confirm whether the 85 has one from what I have read the injecters are powered by the fuel pump relay and controlled by the ecu dose that mean if no power then it is the relay or dose the ecu fire the relay cn yo jump them like the fuel pump

 

I don't have any wiring diagrams for 740s other than 91+, so I can't confirm anything.

on the 91/92 740/940, the 'radio interference suppression relay' was controlled by the main EFI relay, NOT the fuel pump relay, however, on a 1984 240 (which I do have schematics for), the injectors are powered off the fuel pump relay.

 

thanks again. I will post when I can isolate the power issue.

 

http://www.davebarton.com/fuelpumprelaymodlhjet.png

 

I think that mod is a little silly, unless you really can't afford to replace a volvo LH relay every 15-20 years. with the mod, you'll still need a good one, but you'll eventually need to replace the other relay you used, which yes, is presumably a cheaper relay.

 

I just was using the info about what the pins do on the relay there is no power at pin 30 and that may be my issue. I should have posted that in the first place.

 

on a 740, that pin 30 should be coming directly from fuse 1, which in turn gets power directly from the battery.

 

Thats what I was hoping! will be working on it today and will keep you posted.

 

Well my dyslexia rares its head again 30 is the only pin that has power I read somewhere that two should any guesses which other one should have power. wire colors don't match the diagram either pin 87-2 should power the injectors and the fuel pumps per this diagram so when I use a jumper to turn on the fuel pumps there should be 12 volts constant at one side of the injector, is a loose wire probable or dose that power come through the ecu.