It's a 1990 740 N/A with the rex-regina fuel system. A few years ago, I spliced in a fuel pressure gauge permanently so that I could constantly monitor the pressure. Apparently, some time this week it became handy.

I noticed that the car was harder to start after sitting for a while and that the performance seemed a tiny bit off. Today, I decided to see what was going on. Normally, when I turn the key into position 2 (or is it 3? the one where all the dash lights come on), the fuel pump primes and the pressure gauge shows a steady reading of about 40PSI or so. Today, when I primed it, the pressure went up to 40, and then in under 2 seconds it dropped back down to 0. Not good.

The car runs fine once it gets started, which to me indicates that the leak is very very small.

I tightened the clamps around the pressure gauge splicing to make sure it wasn't leaking there. There are no apparent leaks (no smell) so what could it be? I'm going to take it to my mechanic on the weekend and have him tighten/doublecheck the fuel filter area. I'd do it myself if I had the time but recent employment change has made it more difficult.

Do Regina systems have a fuel pump check valve? I know the bosch system does, and they have two pumps, but I think I remember someone also saying that the regina system has a check valve and it's a part of the single in-tank pump.

Any suggestions would be greatly appreciated!

edit: Oops, almost forgot to mention. I unplugged the vacuum line in the FPR and the pressure goes up a tiny bit as a result. No fuel in the line.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

I disconnected the fuel line from the fuel rail and then plugged it (the line) with my thumb so that there was a very definite very tight seal around it. I know my thumb wasn't leaking. Then I had a friend turn the key to prime the system. Again, the pressure went up to about 40-50PSI when it primed, but dropped back down to 0 within 2 seconds.

That being said, tomorrow I need to make sure that the gauge isn't somehow leaking.

I mean... it's starting to look more and more like the fuel pump, or the check valve that's integrated into it, because if it were actually a leak like this would cause fuel to actually come out from SOMEWHERE in the system, and I'd smell or see it.

Any opinions?

Thanks for all the help so far!!
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

You have a bad check valve in the fuel pump. The check valve is supposed to hold pressure in the system. I have changed these in the LH systems with two fuel pumps. The check valve is in the main fuel pump, under the car, in LH systems. In your car, there is one fuel pump in the fuel tank.
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john

John, is it possible to just replace the check valve or do I have to replace the entire pump? Also, are there any ill effects from leaving it as is for a while?
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

I don't know if you can separately replace the check valve on the Regina in tank fuel pump, but I suspect that you can. My computer is at the shop, anbd I cannot access Vadis to find out.

A bad check valve only gives slow starts in my experience, that is it.
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john

Hmm okie dokie. What about in the winter, any worries there?

P.S. Sorry I wasn't able to work out your computer prob. Shoot me an email with an update.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

The Rex/Regina Fuel greenbook makes no mention of a check valve when diagnosing loss of "residual pressure". It just says to check for injector leaks or replace the Fuel Pressure Regulator.

Could that be why the Regina has a different FPR? With a check valve in it?
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

The check valve has to be on the supply side of the system. It will be part of the in tank fuel pump assembly.

The fuel pressure regulator is the same, or will interchange.
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john

I don't think so. The FPR appears to be working fine, and I've also read on this board of many people replacing their regina FPRs with the cheaper Bosch FPRs and they didn't experience any probs. Anyway, I eliminated the FPR from the equation anyway when I disconnect the fuel line and used my thumb. It has to be somewhere to the 'rear' of the fuel rail (fuel filter, fuel pressure gauge, fuel line, or the pump.)
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

Two things strike me odd. One, if you are holding 40 psi with your thumb the regulator must be part of the equation, I'd think, because the pump itself should be able to develop much more. So if you spliced the gauge into the feed to the rail, where are you putting your thumb where it would both be regulated to 40 by the FPR and eliminating injector leakage as a possibility. And two, if you clamp the return line (thumb in pocket) does it still drop pressure?

Sorry if this is a dumb question - I tried to read all the posts carefully.

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Art Benstein near Baltimore

I disconnected the line from the fuel rail, so I'm holding the 40-50PSI with my thumb on the line that comes from the fuel filter located under the car.

The only thing connected to that line is the gauge, the fuel line, the fuel filter, some more fuel line, and then the intank pump. The return line isn't part of it nor is the FPR, or the fuel rail.

I should note again that I only primed the system to check the pressure. In other words, while I had my thumb over it, I had my friend go to the ignition and turn it to position 2 (or 3... the one with the lights on). In this way, the pump only primes for a brief moment to develop pressure. I'm sure the pressure would have been much higher if he actually started cranking away and the pump remained on the whole time.

There are no dumb questions, only dumb people. ;-) (just kidding)
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

Ok, I see now. But the picture that keeps coming to mind on this hot day has me holding back with my thumb the 40 lbs of well-pump generated water pressure in the garden hose. Someone standing nearby is going to get cooled off!

Guess I'd rather see you plug that securely and run the pump via bypass at least a few seconds, as long as you have a gauge in place, but I'm just trying to exhaust all possibilities you don't have to pull that pump, which by now is looking inevitable. I've got no experience with a Regina pump, so I'll quietly bow out now.
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Art Benstein near Baltimore

Art, you need to remember that a garden hose is much wider and bigger so there's more pressure overall that you have to hold in. The fuel line is pretty tiny. :)

I unfortunately don't have a plug for the line with a sealed end so this will have to do, but I did do it a few times and listened for leaks from my thumb and what not. It was definitely a tight seal.

I'm thinking I might not pull the pump for a while. A replacement from FCP runs about $95, and I really don't have time to do that yet. I'm still waiting for my headliner material to arrive from the store and I need to tackle that first. It's horrible in my car right now with the headliner drooping. Yeah, that's an aesthetic problem as opposed to a functional thing (fuel pump) but darnit, it's annoying. I can deal with cranking the car a tiny bit longer. :)

BTW, don't bow out. The chit chat makes for good entertainment!
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

Oops, I guess I missed your response. Had to tell you it had me smiling, especially calling me on my fallacious garden hose metaphor, because it reminds me of my own attempts to clarify electrical phenomena with the voltage~pressure current~flow volume analogy. The real reason someone gets wet is my thumb isn't that big.

The headliner coming down would be a biggie for me too. Seems like this summer the spider population has exploded. Everywhere I walk outdoors in the morning, even indoors. Has me scratching my head a lot thinking there's a whole new baby spider family trying to make a home. The headliner touching my head would have me crazy.

I hope you take some pics of the Regina pump should you wind up pulling it. I don't believe I've ever seen one.

Invar - yep - sounds like your fuel pump. Just curious, how old is the current fuel pump? I'm too lazy to go through all your project pages to find out.
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Tony - 1990 745 - 225K Regina Non-turbo

Ha, the pump is the original as far as I know, unless the previous owner replaced it some time before 1997 when we acquired the vehicle. :) So it's 14 years old!
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

Although I am not familiar with the Rex Regina system it almost surely has a check valve after the pump to maintain fuel rail and line pressure for a while after shut down to prevent vapour lock (that is the main purpose of the c valve). I should think that an injector leaking down would not drop the fuel pressure in 2 seconds and if it did you would experience other driveabilty symptoms caused by severe flooding of fuel into that cylinder. However a bad check valve one engine is running would not affect driveabilty in any way.
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David Hunter

this weekend, i'm going to disconnect the line from the fuel rail, cover up the opening with my thumb (40psi isn't that much, i've held more with my thumb before) and see what happens to the pressure. i guess that'll help narrow things down a tiny bit?
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

I didn't think if the injectors, but that would fit the symptoms too. If it's one of te regular injectors, you might be able to narrow it down by just priming the system with the key but not starting the car and then removing each spark plug and smelling it. Normally, they wouldn't be wet or smell much like gas.

You could also pinch off the hose to the cold start injector (with a C clamp or something) and see if the system holds pressure to eliminate or blame that.
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Andy in St. Paul, '91 745 Regina 194K mi, '89 244 138K, '87 245 RIP

The Regina greenbook, under Residual Fuel Pressure test says it "should drop below 29 psi in less than 20 minutes". If it drops too fast (like yours) it says to check the injection and cold start valves—if OK, test again with a new Fuel Pressure Regulator (which seems the more likely possibility to me, on a hunch).
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

If it's like the bosch, the valve is the end nipple on the fuel pump and can be replaced but it is expensive from volvo and is more cost effective to replace the whole pump with new valve.

Invar - whether or not the Regina system has a check valve, I can't say. But, if it does, I can tell you where it is NOT. I replaced my fuel lines recently that are out of the tank to the filter and then fuel rail. No valve in those sections.

Tony
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Tony - 1990 745 - 225K Regina Non-turbo

I know that on some cars it is inside the pump housing. So I assume that you would have to replace the whole pump if the valve is in there and it's bad.
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Andy in St. Paul, '91 745 Regina 194K mi, '89 244 138K, '87 245 RIP

What if it is the fuel tank that can't hold the pressure ? The return line is open to it. If so, it could just be the cap. Got another cap to try ?
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Andy in St. Paul, '91 745 Regina 194K mi, '89 244 138K, '87 245 RIP

the fuel tank has no "pressure"

The return line from the fuel rail is open to the tank, isn't it ?
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Andy in St. Paul, '91 745 Regina 194K mi, '89 244 138K, '87 245 RIP

It is but that has nothing to do with the pressure. :)
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

Ok. Then explain it to me. There is pressure that is supposed to remain in the fuel rail, the fuel rail has an open hose to the fuel tank (return line) and the tank isn't pressurised too ?

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Andy in St. Paul, '91 745 Regina 194K mi, '89 244 138K, '87 245 RIP

Nope, tank is never pressurized, fuel rail pressure is isolated from the the return line. That is how the fuel pressure regulator is plumbed, if you have a look at it. In fact the tank is vented via the evap system.
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David Hunter

I also have a Regina, but have never had to fool with my fuel pump so I am interested in the information you get here. I do believe that there is only one pump.

I also think that there must be a check valve somewhere (either in, or near the pump) because you want the pressure to stay up after the car is shut off so it will restart quickly.

If your pressure goes to zero in two seconds after the pump stops, that seems like a fairly substantial leak. Certainly enough to smell it if it were coming out of the car. So it seems to me that the check valve is the likely culprit.

Just my thoughts.
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Andy in St. Paul, '91 745 Regina 194K mi, '89 244 138K, '87 245 RIP

if you find out anything please post it, I have been fighting the same problem for a while. I couldn't pass emissions in Arizona because the fuel pressure failed. The only thing I have left to replace it the line from the fuel pump to the fuel regulator and the fuel inj's.