Best way to measure fuel pressure while driving

[lippy]

I want to check fuel pressure under load at WOT. Of course I've checked it at my regulator with a mechanical gauge revving the engine. What's the best setup to check pressure while driving? I don't really like the idea of running a tube filled with gas inside the car - even temporarily. I suppose I could get an electrical pressure sender and gauge but that's a lot of work and expense for something I won't keep in the car. Any experience/help is appreciated. Thanks.

[Jerry Clayton]

On my pro stock race car with dual dominators I put an electric sending unit in one of the fittings of the Holley float bowl and used an electric guage-no leaks,easy to pull wire when working on carbs/engine and you can remove interior guage any time you want-
run one wire thry firewall loom to go to sending unit, plug the guage into cigar lighter---------and no I didn't have a cigar lighter in a race car---I'm not Dick Landy

[patrickt]

Put a temporary mechanical gauge under the hood and zip tie your phone, with the flash light in the "always on" configuration, pointing at it taking a video. Then get on a safe road and WOT it. The audio of the vid will tell you when that's occurring and you can see the what the needle is doing during the WOT event.

[pats401]

they make an isolator,fuel goes to rubber bladder in the unit,and from there to the guage tube is filled and blead with antifreeze,safe . pat.

[bobcowan]

I used a See-Snake and some masking tape. https://www.ridgid.com/us/en/inspection-cameras

I use this tool for all kinds of stuff - very handy.

[Frank Messina]

You could mount it to the cowl in front of the windshield.

You'd just have to be creative on how to get the line up there without pinching it but shouldn't be too hard. As far as the mounting bracket goes there are a number of possibilities since you're only talking temporary.
Frank

[BOBOCobra]

Run a regulator after your fuel rail and a return line to the tank and never worry about it again. If your having fuel delivery issues this is your best fix so just do it right and sleep easy.

[patrickt]

You know, on the dang few times I hit WOT, the last thing I want to do is look down at a gauge....

[lippy]

I ended up buying a stainless braided hose and temporarily running it into the passenger compartment, and using the same mechanical gauge I use on my regulator. Drove around with it for a half hour and fine tuned the pressure. It did drop about a PSI when hot, but still adequate. I have it set for 6.5 cold and 5.5 hot, and it maintains pressure even under throttle. Removed the hose and gauge, all set.

[Jim Doak]

If you have a liquid-filled gauge just be aware that the gauge pressure will change (drop) as the gauge temperature increases. (Not that the actual fuel pressure is dropping, just the pressure displayed on the gauge.)

I've learned this recently from chasing an actual fuel delivery problem. It's caused from the gauge referencing the pressure within the gauge liquid instead of referencing atmospheric pressure.

If you have a liquid-filled fuel pressure gauge located in your engine compartment you can perform a little experiment like I did. Check your fuel pressure when you first start your engine then check it again after the engine compartment has warmed-up. If it reads lower when hot as compared to cold, with the engine running pour some cold water over the gauge and check the pressure. You may be surprised and see the displayed gauge pressure increasing as the gauge temperature decreases.