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I tried hooking up my fuel pressure gauge to the schraeder test port at the back of the engine the other day, but I couldn't get the pipe to hook up. It seems like the centre of the valve sticks out too far for the pipe on my gauge to get a grip on the threads.
Could you recommend me a gauge that will hook up to a P38 Thor?
Cheers
Morat

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Hi Morat, I’ve got this one and can confirm that with one of the included adapters it threads on to the test port without any problem. The extra hose length is nice for watching the gauge while you’re in the cab cycling the engine. Came in a terrible plastic pouch thing but it doesn’t get used much.

I’m sure they sell this or a clone just like it which ever continent you’re on!

Actron CP7838 Professional Fuel Pressure Tester https://www.amazon.com/dp/B0009XQUKC

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I just use a tyre pressure gauge but it's going to depend on what fitting it has for the Schrader valve.

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You could use a schraeder valve tool to remove the valve temporarily while you have the pressure gauge connected. Some such tools look a bit like a radiator key but with a forked end.

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Lpgc wrote:

You could use a schraeder valve tool to remove the valve temporarily while you have the pressure gauge connected. Some such tools look a bit like a radiator key but with a forked end.

Example of them on this Amazon listing
https://www.amazon.co.uk/pengxiaomei-Valve-Repair-Single-Remover/dp/B07T6SF2N5/

I think you'd find the screwdriver type a bit easier to get onto the port though that kit includes both types.

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Any issues prompting you to measure petrol pressure Morat?

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Lpgc wrote:

You could use a schraeder valve tool to remove the valve temporarily while you have the pressure gauge connected. Some such tools look a bit like a radiator key but with a forked end.

That's a good idea! Certainly worth a shot before splashing out again. I'll just make sure to do it from cold ;)

And yes, I'm having some weird starting issues from cold. Warm restarts are 100%, cold starts take a lot of faffing about. It seems to start much more readily if I run the fuel pump between start attempts so I thought I'd better measure the fuel pressure and see what's going on at the rail.

From cold it cranks, stumbles, stops and after I run the pump I've got about a 50% chance on each subsequent crank of it stumbling again, or starting as if nothing had happened.

I've had some misfire issues last year so I replaced the coil packs, plugs, and wires which seemed to sort it out. Then the issues came back with cold weather and gradually spread to all the time. I have the odd misfire code (unsurprising) and the occasional serial link error for the antitheft but they occur far less regularly than the starting issue so I'm not sure if they're related or it's a multi-factor problem. The fun continues :)

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I had a similar issue on a Dakota I used to have. The check valve in the fuel delivery leaked down, so cold starts had no residual fuel pressure. In my case the valve was part of the fuel pump. I’m not sure if the P38 check valve is in the pump or not. But this may not be your issue at all.

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Yeah, that's probably it. I just want to confirm what's going on before I get into dropping the tank or cutting a hole.
Of course, I went to it yesterday and it started from cold on the first hit. You gotta love 'em ;)