So, I'm poking around the area where my fuel filter is and I notice a schrader valve on a T inserted in-line in the fuel line going from my tank to my main (external) fuel pump. I suppose this was installed in order to test the pressure from the transfer (in-tank) fuel pump. My question is, How do I go about making use of this schrader valve if I want to check the pressure of my transfer pump?

 

Answering my own question, but now the info is here for all to see.

Apparently folks got tired of disconnecting fuel lines and inserting uber-expensive fuel line pressure gauges into the fuel lines. So someone (I'm guessing Volvo) installed schrader valves at strategic locations. Not only do I have one on my fuel line between my transfer and main fuel pump, but there is also one on my fuel rail. (I just had to run out and check.) It looks as if it was manufactured with the valve right on it, not an after-market add-on.

So now it will be much easier to troubleshoot my stalling problems (better left for a different thread). All I need to do is get a standard pressure gauge made to fit on these schrader valves and I am good to go. Knowing for sure whether or not I have enough fuel pressure will be a big help in narrowing things down.

 

let us know what gauge worked for you

 

Well, I grilled the experts at my the Alameda Napa store (they really are pretty knowledgeable) and they tried to talk me out of even buying a fuel pressure gauge. The only ones he could find in his book were $75 and up, all with lots of connectors and adapters. All I need is a gauge with a hose and a connector on the end to screw into my schrader valve. Maybe a pressure bleed off hose, for good measure, but not necessary. For my purposes, it needs to read from 0-100 psi.

Anyone have any recommendations on something that might cost me closer to $40 or less?

 

you realize pressure bleedoff for fuel means squirting fuel out? eek.

the couple times I've wanted to confirm fuel pressure, I've swung by my favorite mechanic with a 6-pack, and he's hooked up his gauge and read it for me.

I think I did see a t-fitting-to-nowhere on the fuel line near the main pump last time I was looking at the parts diagrams, but I forget if that was for a 240 or 940. ah, here it is on a 1992 940. '3507386', and the Note says "With service socket-evacuation valve", and its on the RETURN hose back to the gas tank. maybe its used in manufacturing to vacuum test the fuel system before any fuel is put in, or something?

 

Yes, that is why the hose is long enough to put the end into a receptical to catch that squirting fuel. You can see them on in the pictures on-line. Here is a picture of one.

Nope, my schrader valve is definitely right in the hose from the fuel tank to the main fuel pump. Why anyone would want or need to bleed pressure from the return hose (which just has an open end in the tank) is beyond me. It wouldn't remove pressure from the main lines at all, unless A) the fuel pressure regulator was hosed and B) the return line was completely plugged. Of course, that is about as likely as finding a 240 with under 50k miles on it.

The guy at the parts store also suggested asking a mechanic to do the pressure test for me. But I don't know any that will work for beer. And by the time I paid him for the all the tests that would need to be done - at both test points, plus before and after any repairs - I could have bought the gauge.

So, I guess I'm heading into uncharted territory here. I'll let you all know what I find out.

 

I decided to order the . It got pretty good reviews and is one of the few sold by Summit racing. It was just $10 cheaper at Amazon and I get free 2-day shipping. I'll let you know how it works out.

 

OK, so the fuel pressure gauge came today (see above for link). On the end of the hose, the fitting is what they call a "large schrader" connector. However, the kit comes with an adapter (which they call the "Ford" adapter) for connecting to a regular schrader valve.

Because of the additional adapter required, I had difficulty getting it connected to my schrader valve on my fuel rail. Who oh why couldn't Volvo have made that valve point in some direction that was unobstructed? As the engine was still pretty warm, I didn't want to fight with maybe wrangling it on there. I will wait till I can do it when the engine is cool and then let you know if I could get it on at all. I may need a right-angle adapter.

Now, I was able to get it connected to the T connector in the fuel line between my tank and main pump. However, it didn't read any pressure at all. I will save any troubleshooting of my car for a different thread but I will say that I was able to get a small dribble of gas to come out of the schrader valve while the engine was running and by holding open the pressure release valve on the gauge, I was able to get a tiny amount of fuel to into the gauge's hose. So, I am pretty sure that if there were pressure in the line the gauge would have had a reading.

I know that 4-5 psi is not much compared to the 30-40 psi I am supposed to have up top, but if there were 4-5 psi in the fuel line, I would think that it would have at least squirted out when I pushed in the valve release on the schrader valve rather than just a tiny dribble that barely dampened my fingers. In fact, I could swear it was sucking air some of the time. Yes I know all this indicates that my transfer pump is not working, but the point I am getting at here in this thread, is that I seriously don't think there was any pressure to read, so the gauge was actually accurate even though it showed a reading of zero and never budged.

Of course, I only just now realized that I could simply remove the valve-stem from the schrader valve, connect the pressure gauge, then start the car and take a reading without worrying about if the valve itself is the problem. I will try that tomorrow but I'm guessing I will get the same result. If there were any pressure at all and the schrader valve was only opening a crack then I would have gotten a little squirt instead of a miniscule dribble.

 

nice.....I have seen this gauge in a local store but thought it would not work.....the free shipping is nice....thanks for the research and post

 

Well, yesterday, after work, before driving home and getting the engine all hot, I tried to get the fuel pressure gauge connected to the schrader valve on the fuel rail. Try as I might, it just wouldn't quite fit. The fact that the connector on the end of the hose is a "large schrader" and requires an adapter, pushes the whole thing down too close to the intake manifold. Of course it would fit just fine if the existing schrader valve on my fuel rail didn't point almost exactly at a bolt head sticking up out of where the manifold is bolted to the head.

I will have to find a right angle adapter somewhere. If I find one, I will let you know where I find it.

 

I honestly don't think that schraeder on the fuel rail is intended for measuring fuel pressure... the parts lists describe it as a 'evacuation port', which I'd bet is used for testing the fuel system integrity prior to putting any fuel in the tank.

 

And you are doing all that because of an intermittent stalling problem?

 

hello all.

my 1990 240 is leaking from this valve. Is the valve stem of a grade that can handle fuel, or can I use any type that fits?

 

the rubber stuff would have to be Viton or another fuel safe rubber grade, which I bet your average tire valve isn't. ditto the cap.

sadly, my volvo parts catalog shows the part in the drawing but has no line item for it, implying its no longer available from the mothership.

I dunno, I think I'd try a local generic/import auto parts store, odds are pretty good they'd have something. "Viton" is the key word, thats fuel safe synthetic rubber used in o-rings.

 

fuel gauges can be rented free at:
Fuel Pump Diagnostic Kit | AutoZone.com