Clear answer time: How do you determine whether an M30 Fuel Pressure Regulator is bad

[nm735]

Hello,

I have been trying to fix my car for the last year, and I have finally gotten the stupid thing running and driving. It now lean surges. Barely noticeable, and it doesn't have much power in the upper rev range. It also bogs down under full throttle from a stop. This bugs me because I just got beat by a kid in a surplus cop car. When I was fixing it before, I checked the fuel pressure. I did this by jumping the relay. At the time I performed this test, the car would not start. I have checked for vacuum leaks. There do not appear to be any. My question for you is how do I test the Fuel Pressure Regulator on a car equipped with a BMW M30, specifically one equipped with a 4HP22. They do not like to rev in park.

THINGS I DO NOT WANT
- People arguing over whether or not you can get injured doing a fuel pressure test
- People suggesting alternatives to the fuel pressure regulator. I will address the alternatives after I have ruled out the fuel pressure regulator.
- People telling me to take it to a mechanic. This has not really been an issue on this forum, but I actually ran across this on a Jeep forum.

I look forward to your responses.

Thank you

[SergeBMW]

Buddy, lets just start here...

You have 12 posts on this forum, which all look like they were you asking for help so you have not even contributed to this forum. You come in here and DEMAND a clear cut answer to your problem, and on top of that you WRITE IN CAPS THE THINGS YOU DO NOT WANT.... A forum is used for troubleshooting issues, no one can give an exact answer every time. I suggest you do not come in here and demand answers because you wont find any. This is not a test and you are not any higher than anyone here.

Also, I do have the answer you need but ill hold back in giving that info out to you just because of your attitude, maybe someone else can chime in.

[SergeBMW]

There is no problem with asking for help, its just the way you come in here demanding only the right answer you are looking for and god forbid, anything else. That's what it was, if you came in asking how to do it without all the extra BS I would have give you the source for the information needed for you to conduct the test. Simple.

[nm735]

My apologies. My bad for thinking this was a place to get information. I'm sorry, I didn't know I had to brown nose by giving useless feedback to people who don't need suggestions such as "Well, did you check the battery?"

God forbid somebody actually try to help me on this forum.

- - - Updated - - -

I asked for the test. I didn't want anybody to try and help me diagnose my problem. I wanted to know a black and white procedure. That is pretty clear cut. If you asked somebody how to use a microwave, and they suggested that you instead try a toaster to heat your left-overs, you'd be understandably upset. That's pretty much all I get out of forums. I rarely post and only do if the information is not available elsewhere. And then I try to word my questions in such a way that they will be useful to others with the same questions.

[SergeBMW]

Im thinking you like the idea of brown nosing... You do speak quite a bit about it

You seem to have had a lot of bad experiences in forums, I wonder why. You still are not understanding at what I was trying to explain to you, oh well.

[shogun]

trying to help, I searched, how about this thread https://www.bimmerforums.com/forum/s...re-on-BMW-735i
The M30 fuel pump is originally Bosch 0580464995
operating pressure is 3 bar
conveying capcity at 12 V 1.9 liter/minute
conveying capacity against counterpressure 875 ccm/30 seconds
Power consumption is 5A

https://www.bimmerforums.com/forum/s...e-test-results

[nm735]

I mentioned it once. And yes, I do understand what you are trying to say. I'm saying, in light of the uselessness that permeates the answers in this forum, that perhaps you shouldn't make a point about respect, when such respect only perpetuates the uselessness of those answers. I was trying to help create a clear answer, that way, somebody who comes by in a few years doesn't find a forum that describes exactly what they are looking for, followed by everybody ignoring the question.

You've done wonders, making me feel like this is a welcoming and useful resource.

[nm735]

@shogun Thank you. This is precisely what I was looking for. I will update.

[shogun]

Checking fuel pressure fuel pump engine BMW M20, M30, M40, M42, M43, M44, M52, S38, S50, S52 https://bmwtis.info/checking-fuel-pr...2-s38-s50-s52/


Testing for a leaking, ruptured, fuel pressure regulator diaphragm
That is a good analysis. How to verify the cause of an intermittent long crank and a start/stall condition. No need to have the electronics as shown first (because we backyard mechanics do not have them anyway), just remove the vacuum hose and sniff if there is fuel smell or even fuel coming out. Watch for fuel. Takes over a minute that fuel is coming out of the port in this vid, diaphragm cracked. https://www.youtube.com/watch?v=AKtR_yF7bi8
To be on the safe side, I would connect on the fuel pressure vacuum connector a transparent hose and lead it out of engine bay into a container/bottle, just in case a lot of fuel is splashing out.

[whiskychaser]

My preferred method is to use a fuel pressure gauge and a vacuum gauge. On the M30, you put the pressure gauge inline at the back end of the fuel rail. I know what the pressure is for the M50 but somebody will jump in or you can just search what the pressure is for the M30.

Jumper the fuel pump relay and check what pressure you have. Remove the jumper and start the engine normally. The pressure should go down. A rule of thumb would be about a half a psi for every inch of mercury vacuum at sea level. So if you are pulling 18 inHG, your pressure will drop by about 9psi. If you now pinch the vacuum hose, the pressure should go back up to what it was when you did the static test. You can also do the static flow tests and residual pressure tests as outlined in Bentleys

[nm735]

UPDATE

I have performed the tests, and I am now certain that the fuel system is in good working order. Fuel Pressure with the relay jumped is about 45 PSI. It holds pressure after the pump has stopped. When running, the car has a fuel pressure around 35-37 PSI. It jumps to about 46 with vacuum to the regulator removed.
The results of my test were close to what this person saw. https://www.bimmerforums.com/forum/s...e-test-results

I believe the fuel system, specifically the fuel pressure regulator, is in fine working order.

Your responses have been helpful. You have saved me 40 dollars. If anybody has any questions about the procedure, I will be happy to answer them.

[whiskychaser]

Altitude affects intake vacuum by about 1 inHG for every 1000 feet above sea level. So where you live, you might expect it to be 4 inHG less than at sea level. That could of course have an affect on fuel pressure. Your readings appear to be quite normal

[CamE32]

Make sure there's absolutely no fuel in the vacuum hose. That was the only way I knew for sure that mine were bad. Swapped in a no-name one from amazon for $25 and haven't had a problem since.

[Annddrriy]

M30 engine automatic trany. How does fuel shock absorber works in the fuel tank witch is located on top of fuel pump it make any changes for fuel delivery engine running some times rpm up and down after when shift gear from D to N ? Thanks in advance !

[shogun]

fuel shock absorber? I assume you mean fuel check valve. The fuel pump has incorporated in the outlet of the fuel pump a check valve, that let's the fuel flow only in direction towards the engine, when the engine is stopped, the check valve automatically closes by the pressure in the fuel line between fuel pump and engine bay. When engine is running, the check valve is open again by the pressure from the fuel pump. Your problem is not related to the fuel pump check valve, the fuel pressure regulator in the engine regulates the flow of the fuel to the injectors. If you have a vacuum leak in the vacuum system, then the fuel pressure will change http://www.nmia.com/~dgnrg/hose_map.jpg
https://www.bimmerforums.com/forum/s...9#post30640189
Have the engine smoked for intake leaks, and check/clean the idle air control valve.

you also have to check the throttle safety clips. Maybe broken http://www.nmia.com/~dgnrg/tc2.jpg DIY https://www.bimmerforums.com/forum/s...epair-for-1-72

[Annddrriy]

Not fuel check valve. Fuel shock absorber witch is atouch on top of fuel pump after check valve it is last part seating very top on fuel pump looks like mushroom it make any changes for fuel delivery or adjust pressure to the engine bay engine running some times rpm up and down after when shift gear from D to N and than after 30 seconds rpm go back to normal. Some one call it Fuel Tank Pump Surge Damper. Thanks in advance !

[shogun]

I see, you mean item 15 absorber 16141179281 http://bmwfans.info/parts-catalog/E3...nk/#1179281_15
I have never seen and disassembled one, my 750 fuel pumps do not have such absorber, apparently only the the 730/5 M30, also used on E34 M40, M43, M20, M30, M50, S38.
Anyway, whatever the absorber does, in the end the fuel pressure regulator in engine bay regulates the pressure and the volume of the fuel coming into the injectors.

[Cactuar]

From research online, it is a fuel pulsation dampener and it does not regulate fuel pressure:

A fuel dampener (sometimes called a fuel damper) is a device that dampens (or softens) pulsations in the stream of fuel caused by the fuel pump. This is to reduce hydraulic "noise" in the fuel rails and provide a smooth stream of fuel to the injectors--the constant pulsating caused by the fuel pump would otherwise create a slight "ripple" effect inside the fuel system which could potentially disrupt adequate flow of fuel to the injectors.

The fuel dampener consists of a diaphragm and spring, similar to a fuel pressure regulator. However, it does not regulate pressure, and the vacuum-adjustable diaphragm assembly exists to act as a variable "shock absorber," so it can absorb pulsations in the fuel without impeding the flow of fuel to the rail.

Note: While similar in appearance, the fuel dampener should not be confused with the Fuel Pressure Regulator.