Just bought a 740, can"t keep started.

zcobramike · Post by **zcobramike** » 21 Jul 2006, 14:09

I just got a 91 740 that will not run. It had a dead fuelpump so I replaced it , along with new plugs, and battery. It will only start with starting fluid- then run very roughly maybe getting to 2 on the tac. as long as I pump the gas pedal violenty then it dies. what could be the next things for me to check? thanks, mike

Post by **billofdurham** » 21 Jul 2006, 15:23

Sounds like you have a fuel problem. First thing to check would be the in-line fuel filter. It is often overlooked on the services.

Bill.

wojeepster · Post by **wojeepster** » 21 Jul 2006, 15:30

fuel pump relay white relay 2nd row behind ashtray
in tank pre pump
Main fuel pump

Kmaniac in California USA · Post by **Kmaniac in California USA** » 21 Jul 2006, 17:55

Your car has TWO fuel pumps, one in the gas tank (in-tank) pump and one under the car (main fuel pump). If you replaced the main fuel pump without replacing or even inspecting the in-tank fuel pump, you may have just destroyed the new main fuel pump.

First, check the fuse for the in-tank fuel pump. If blown, you definitely need to replace the in-tank pump and filter sock.

Next, remove the sender unit assembly from the fuel tank and inspect the filter sock on the pick up on the in-tank pump. If it looks the least bit deteriorated or has any holes in it whatsoever, it is time to replace the in-tank pump and filter sock AND the main fuel pump, regardless of age.

A hole in the pick up filter sock will allow dirt and debris in the gasoline to foul and irreparibly damage both fuel pumps. The main fuel filter only protects the underhood components. For more information, search this forum for my experiences with my fuel pumps.

zcobramike · Post by **zcobramike** » 25 Jul 2006, 10:22

I have replaced the in tank pump-although both the relay and fuse was good- but where is the second outside pump located?
thanks!

Kmaniac in California USA · Post by **Kmaniac in California USA** » 28 Jul 2006, 09:18

The main fuel pump should be next to the fuel filter, under the car below the driver's seat. Take a look and let us know what you find.

zcobramike · Post by **zcobramike** » 28 Jul 2006, 19:57

I notice there is a large in line filter under the drivers side of the car; but no other fuel pump. I believe I have only the one in the tank. Therefore what I plan to do next is use a pair of good snips to cut the fuelline just after the pump heading toward the engine and put the lines in a plastic jug. Then I plan to turn on the key to see if indeed my new pump pumps gas into the jug. If not I will cut off the fuelpump and try again to see if it works. ~What do you think of this method of checking the fuelpump and filter? -M.

Volvo Tech1975 · Post by **Volvo Tech1975** » 30 Jul 2006, 23:51

You may want to try disconnecting the MAF (mass airflow sensor)... they are comonly problematic and without the proper test equipment hard to diagnose. If you unplug it and the car starts, that might just be your problem.

cosmiclobster · Post by **cosmiclobster** » 31 Jul 2006, 19:19

I would also try the MAF or AMM (Air Mass Meter). Unplug it and your car will go to a default mixture mode. If it runs with the AMM unplugged, then the problem is the AMM. The AMM is in line with the air intake just before the intake manifold.

To check the fuel, it is easy to remove 3 bolts that hold the fuel rail and fuel injectors in place. On a cold engine, remove the rail and have someone crank the engine for a second or two. I suspect that the fuel pumps are O.K. and the fuel should squirt a few feet! It if does then your entire fuel system is working O.K.

Hope this helps!

cosmiclobster · Post by **cosmiclobster** » 31 Jul 2006, 19:22

P.S. The 2nd fuel pump is on the same tray as the big cylinderical shaped fuel filter.