Sometimes when I have driven the car and it is up to temperature, then I shut it off – when I return to start it again, I need to wait about 10 minutes to restart the engine. There is really no pattern to when the starting problem might occur. And a couple of times the engine just quit while driving. Then I have to pull off to the side of the road and wait the 10+ minutes and it starts right up. There is no indication the car has overheated. The needle is usually half when this happens. The starter is fine – just won't fire as if there is no fuel. Do you think it's a fuel pump or filter problem?

As fuel pumps are quite expensive to replace, first check the fuel pump relay. The relays are under the fuse tray, the FPR is #103. When it is not starting, pull the relay out and run a wire or paper clip from 15 to 87, that turns the fuel pump on when the key is in posII.

The relay can easily be re-soldered. If you get a new relay, make sure the part number is the same.

Klaus
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1967 220 belonging to C.A. lives on

KlausC,
I ran the paperclip test and the relay seems to be working the same way as the paperclip. There is a buzzing when the posts 15 and 87 are jumped. I opened the relay and there is no indication of a faulty soldering connection. When I start the engine it works fine and after switching off the engine the fuel pump sounds like it continues to run for about 5-10 seconds after I switch it off. Is that normal? I am not sure what to test beyond this? Any suggestions?

Not normal. The fuel pump must turn off as soon as the ignition is switched off, no delay. Are you sure you are hearing the fuel pump and not the idle air motor or the air pump(cold start only)? Flip the rear seat back forward to hear the pump better.

Klaus
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1967 220 belonging to C.A. lives on

That must be some other kind of motor or pump.

When I listen in the trunk, I hear the pump while the key is in PosII. Does it pressurize and then stop once it reaches a certain pressure?

I am still not clear if we have eliminated the relay or the pump. The problem is usually after running for quite a while and on hot days...never while the engine is cool or first thing in the morning.

Would any of this relate to the thermostat? I would think I would see that on the temperature gauge or other signs of overheating.

Do you know the part number for a new relay? I got one yesterday from NAPA that they swore was the right relay. It is not. It's a rectangle and the bayonet probes are round. It does not have 103 printed on top either.

The relay part number is printed on the side of the relay. I believe it is 898.797 for the NA engine. FCP groton has it listed at $35.84 + shipping:
http://www.fcpgroton.com/product-exec/product_id/16640/nm/1993_1994_Volvo_850_Fuel_Pump_Relay/category_id/154

When you first turn the key to posII, the pump should run for a second or two and then turn off.

The problem could be the fuel pump, but you need to check the pressure at the end of the injector rail, after the engine dies and will not restart. If you have an old tire pressure gauge that you don't use any more, that works. The pressure should be close to 40 with a running engine, above 30psi just after the pump is 'primed'.

During your hot no starts, did you try flooring the gas pedal? That turns off the injectors, needed if the engine is 'flooded'.

Try driving around until the engine gets nice and warm, pull into your driveway, and see if it restarts. If not, pull the spark plugs and check them for wetness. Also listen for the pump to prime.

A very dirty fuel filter will cause the fuel pump to work extra hard and possibly over heat, but that condition usually will happen while driving and not after resting a few minutes.

Klaus


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1967 220 belonging to C.A. lives on

What is an NA engine?

The fuel pump does prime when turning the key to posII for about 5-10 seconds [only tried it when cool]. I need to see if that happens when hot.

I have tried flooring the gas pedal. I do notice a slight gas smell in the driver area during one of these episodes. I have also tried half way to the floor. The engine almost starts but will not run...it must sit for 10 minutes or more to cool. The other day this happened and it was almost 100° F and I had to wait until evening before it cooperated.

I thought about the fuel filter being dirty but how could that relate to the temperature issue? And as you stated that's a driving issue not a starting issue...

NA is naturally aspirated, Vs turbo.

I wonder if you have a leaky injector? One injector can flood out 2-3 cylinders at the same time. Hard to check without pulling all of the spark plugs on a hot engine.

Klaus
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1967 220 belonging to C.A. lives on