What are the pressure readings supposed to be on fuel pressure gauge?

[painterdave72]

The shop manuals only have bar pressure as far as i can tell. .i need psi.. thanks!!! Dave...

[Ron]

1 Bar = 14.5 psi

[Jonathan]

The bar is defined using the SI unit pascal, namely: 1 bar ≡ 100,000 Pa. 1 bar is therefore equal to:
100 kPa
1,000,000 dyn/cm2 (baryes)
0.987 atm
14.5038 psi
29.53 inHg
750.06 torr
1×105 N/m2

--------

Whatever you see in the shop manual in bar, multiply it by 14.5 to get it converted to psi.

1 bar = 14.5 psi = more or less one atmosphere (or pressure at sea level of the air above you). This is also the pressure at which you can design a system under to stay out of needing to classify it as a pressure vessel under the ASME code. By no coincidence, this is also what pressure your coolant reservoir cap is set to. Fancy that :)

EDIT: quick fingered Ron for the win!!

[painterdave72]

So my car has 40 psi if i let it sit there with the key on.. and when i start it will be around 50psi and then gradually go up to around 68 psi when warm.. I think these are pretty in spec.. another friend said his car was at around 70 when warm.. could mine be alittle low??

[Bitsyncmaster]

So my car has 40 psi if i let it sit there with the key on.. and when i start it will be around 50psi and then gradually go up to around 68 psi when warm.. I think these are pretty in spec.. another friend said his car was at around 70 when warm.. could mine be alittle low??

About 42 PSI is normal after you shut the engine off. That is rest pressure.

Starting a cold engine the control pressure starts out low about 25 PSI and normally climes to about 50 PSI after a few minuets.

70 PSI is typical primary pressure. Sound to me like your WUR is plugged. Have you cleaned the screen in the WUR yet?

[DMCMW Dave]

About 42 PSI is normal after you shut the engine off. That is rest pressure.

Starting a cold engine the control pressure starts out low about 25 PSI and normally climes to about 50 PSI after a few minuets.

70 PSI is typical primary pressure. Sound to me like your WUR is plugged. Have you cleaned the screen in the WUR yet?

Agree - 70 PSI with the gauge valve open is way too high. It will cause the engine to be very lean, and the CO adjustment will not compensate for this. Classic symptom of a plugged regulator.

[painterdave72]

Okay.. it didnt look plugged.. it has one of the hard brass looking screens in it.. how do you clean it??? And my car is at about 68 when warm and running.. is that still too high?? I thought that was about right? thanks..dave..

[Bitsyncmaster]

Okay.. it didnt look plugged.. it has one of the hard brass looking screens in it.. how do you clean it??? And my car is at about 68 when warm and running.. is that still too high?? I thought that was about right? thanks..dave..

Good question on the hard brass type. I would think you could only clean that by removing that part and revers blowing out with air. Normally there is a fine "window" type screen which can be blown clean from the top. Is your WUR a rebuilt unit? Was it replaced after the tank and lines were cleaned?

[DMCMW Dave]

Okay.. it didnt look plugged.. it has one of the hard brass looking screens in it.. how do you clean it??? And my car is at about 68 when warm and running.. is that still too high?? I thought that was about right? thanks..dave..

Is the valve on the gauge set open? What does the reading do when you close it?

[painterdave72]

HI Dave,, i had it set open cause if i close it it stops fuel from going..if you are talking about the valve in the line part of the gauge..

[David T]

Are you sure all of the fuel lines are hooked up correctly? Recheck their routing. Check the vacuum hoses to the CPR also. If you still have too high a control pressure something is wrong with the CPR. You may also have some kind of a problem with the fuel return to the tank or the PPR may be stuck.
David Teitelbaum

[DMCMW Dave]

Closing the valve on the gauge should not stop the fuel from flowing, I.e. should not kill the engine. How do you have the gauge connected to the fuel distributor? There is Picture in the manual and should have come in the gauge instructions as well.

I'm asking because it sounds to me (hard to tell via email for sure) that you don't have it connected inline with the regulator and are getting the wrong reading.

[painterdave72]

Hi I have it connected exactly as pictured in the book.. my readings are close to what another owner here tested his at a month or two ago...

[DMCMW Dave]

Hi I have it connected exactly as pictured in the book.. my readings are close to what another owner here tested his at a month or two ago...

.............What does the reading do when you close it (the valve on the gauge set)?

[Jonathan]

Hi I have it connected exactly as pictured in the book.. my readings are close to what another owner here tested his at a month or two ago...

Just one possibility here... and this mindset is not unqiue to testing fuel pressures on a DeLorean, but can apply to any measurements being done on anything... is there a chance you could have repeated the same error in this other owners car as you may have in your car? Potentially the instrument you are using could be out of calibration, or may have something not right within its own set-up that is resulting in this same range of readings.

Take a step back and review the measurement procedure and testing devices to confirm that the problem is not related to the test itself versus your car.

A picture or two or video perhaps of what you have there might help confirm things.

[painterdave72]

This is a different gauge.. and the other owner checked his and emailed me his findings.. i think i fixed my problem though.. i took the warm up regulator apart and it is perfect inside so i just blew out the two inlets and ran the car.. it seems to be running fine at the moment. .i will drive it this weekend sometime and let you all know how it is!!!!!! I had to give the pressure gauge back so i couldnt check with the valve closed. but i think all the other pressures are pretty close to what it says in the book....

[Bitsyncmaster]

With your control pressure running up to 68 PSI that would have made the engine run pretty crappy. If it runs good now you probably fixed it. You may want to do a mixture adjustment now that things are fixed.

[painterdave72]

maybe.. the other owners car has fuel pressure at 70 when warm and running.. I thought that was what it was supposed to be?? MIne is around 68 when warm and idleing.... what is yours at Dave...???

[Bitsyncmaster]

maybe.. the other owners car has fuel pressure at 70 when warm and running.. I thought that was what it was supposed to be?? MIne is around 68 when warm and idleing.... what is yours at Dave...???

My car and many others I've worked on all run about 50 PSI control pressure with a warmed up engine. Primary pressure (valve closed, engine off and RPM relay jumpered) seem to run 70 PSI on most cars. I have shimmed my primary pressure for 75 PSI. What do you get during warm up and how long does it take to get up to the max pressure.

[82DMC12]

Hey Dave, I have a true k jet gauge. Let me know if you want me to stop by and we can try it out.
Andy

[painterdave72]

thanks Andy. maybe.. though i took the car out for about a three hour drive today and it ran great.. so far cleaning the warm up regulator seems to have fixed the little bit of sputtering...