Warm up regulator Guru's/Fuel Distributor plunge Sticking

[Peter Seow]

This seems to have contributed to my high system pressure.

The whole problem is the fuel distributor plunger is stuck only when the system is on "On" mode. I just ran my engine for 10 seconds with the new fuel pump i did not want to risk frying the new one up.

Basically low rpm on WOT, was moved from behind to WOT and stil it wont accelerate.

Here's what i test the fuel pressure up is high 1.7 x the normal pressure. The FD is not returning fuel fast enough i only have one gauge i need to retest the Control pressure and return line pressure. And i need to check if the return line is chocked but i doubt it.

Basically the plunger of the FD refuses to move when it is fuel pump is running. but the moment the engine is cut it moves freely, every line to the injector is emitting fuel as per normal.

Now i am wondering whether the WUR, is the cause of the FD plunger binding,

Could the WUR become completely jammed up preventing fuel from coming out of the WUR so there is no fuel in the return line. With the lock in mode it tell the FD plunger to STOP moving. stay there.

I think if i take the FD to bench test it it may not be useful as every injector line is receiving fuel!

I've read on another 924 forum who did the same did have not success with a replacement FD. But it might not have been adjusted

924Board.org :: View topic - Fuel distributor needed urgently

I am wondering if WUR problem can be that servere??

[john walker's workshop]

remove the fittings from the warmup regulator and see if the screen is plugged up.

[Peter Seow]

Thanks have to do that tom.

[Peter Seow]

sometimes throwing money does not work i know because lots of merc owners do that!!

And i do have a merc that i sold. I know the fd may not solve alot of the problems many cis owners are facing.

unless fuel flow is resistricted to some injectors

Benzworld.org - Mercedes-Benz Discussion Forum - Search Results

I hope to update the forum when i solve it.

[boyt911sc]

Originally Posted by Peter Seow

This seems to have contributed to my high system pressure.

The whole problem is the fuel distributor plunger is stuck only when the system is on "On" mode. I just ran my engine for 10 seconds with the new fuel pump i did not want to risk frying the new one up.

Basically low rpm on WOT, was moved from behind to WOT and stil it wont accelerate.

Here's what i test the fuel pressure up is high 1.7 x the normal pressure. The FD is not returning fuel fast enough i only have one gauge i need to retest the Control pressure and return line pressure. And i need to check if the return line is chocked but i doubt it.

Basically the plunger of the FD refuses to move when it is fuel pump is running. but the moment the engine is cut it moves freely, every line to the injector is emitting fuel as per normal.

Now i am wondering whether the WUR, is the cause of the FD plunger binding,

Could the WUR become completely jammed up preventing fuel from coming out of the WUR so there is no fuel in the return line. With the lock in mode it tell the FD plunger to STOP moving. stay there.

I think if i take the FD to bench test it it may not be useful as every injector line is receiving fuel!

I've read on another 924 forum who did the same did have not success with a replacement FD. But it might not have been adjusted

924Board.org :: View topic - Fuel distributor needed urgently

I am wondering if WUR problem can be that servere??

Peter,

You only need one fuel pressure gauge to do the diagnostic tests. Plus you could do the control and system pressure check without even running the engine. So you don't have to worry about accidental fire!!!!! You got to determine your fuel pressures and post the values either in psi or bar. The WUR could be tested and measure the control and warm fuel pressures on a bench or similar set-up.

If the control and system pressures are both excessively high, the fuel return line maybe restricting the return of gasoline to the tank. There are several places where you could do the test. These are at return line from WUR, return line from FD, and at the fitting of the return line to the tank.

Do not replace CIS component/s unless verified defective and avoid the guesswork to save time and money. Keep us posted.

Tony

[Peter Seow]

Return line cleared.. blew air seems cleared ok. i am stuck between the FD and the WUR.

One of these components is bad.

[Walt Fricke]

Peter

If the fuel distributor plunger moves freely with the fuel pump off, I'd not think that it is binding. As long as it comes down when you let the plate fall back to its rest position, it should be good.

But if you have excessive control pressure, then it would be hard (or harder) to move the plunger up.

You do know that the system pressure is set by a regulator screwed into the FD body. It bleeds the excess right back into the return line.

Control pressure is supposed to be set by the WUR (really it is a control pressure regulator). And the top of the plunger is supposed to see only control pressure.

Which is why folks are telling you do to a standard CIS pressure test: what is your system pressure, and what is your control pressure. Without knowing those values you and those who would help are kind of wandering around in the dark. Cold pressures are fine, which you can do by running the fuel pump with the engine stopped (and the air measuring flap in the full down position - don't want to be squirting fuel without the engine running.

Did this motor suddenly start acting up? Or did this happen after you did something to the motor?

[boyt911sc]

Originally Posted by Peter Seow

Return line cleared.. blew air seems cleared ok. i am stuck between the FD and the WUR.

One of these components is bad.

Peter,

How this did you check for the return line? Did you completely removed the complete return line from FD to tank? Or simply the return line from the WUR? What's the build-up fuel pressure you are getting? What's your control and system fuel pressures???? Are you familiar with the CIS fuel line configuration? Keep us posted.

Tony

[john walker's workshop]

did you check to see if the screen in the WUR is clean yet, as i suggested earlier? a blocked screen (particle matter/rust) can cause your problem.

[Peter Seow]

More updates:

Test at return line done after WUR

History of this car:

Owned for 12 long years, still love this car to bits this is my first porsche 911 i got when i won crash in 1998 asian financial crisis testing my uni theory...so hell this car means alot to me.

I done most of the maintaince work myself ya know few out the know porsche and the only one who knows the dealers charges and arm and leg. I 've been the for diagnosis before

I've changed lots as this is my daily driver.

too many sets of tyres three clutches, lots of fuel filter, but lately been going through fuel pumps,

Fuel life would decrease the longer i own the car so i know something was wrong. System pressure was on the high side and would be highest when i accelerate the car.

BUT the car always fires once no second hit on the ignition in it's life but would occasionally stumble when give a hard acceleration from start especially when cold yes it got progressively worst through the years. Occasionally the would be a lean out problem with no power on higher reevs like 6000 rpm, then it fell to 5000 that 4000+, than it got worst and started stalled most the time and would hardly get past 3000 rpm before it failed.

It did have a history of back firing.

NOW back to further test the car. To test the fuel line from the FD outlet would mean i have to remove the fuel distributor...

Yes the control pressure is still higher. probably because the system pressure is high is reading 7 bars. and goes to 8.5 when to reev too 3000rpm. Ok i'll cut the engine at that point to prevent fuel pump damage.

Yes it still fires up straight away. once twist of the key it starts.

Once that 8.5 bars is reached the control arm has problem descending to need to apply excessive force and i dont mean hard here it's really pushing it really hard.

So now it seems more like an FD problem. it's not returning fuel when more fuel is needed.

I am going to do a bench test on the FD. I think the system pressure regulator could be faulty but it doubt the difference in pressure is so significant. Seem more and fed the ever.

I might just order and FD and WUR... it been serving me alot so i am willing to spend on here but i just dont want throw money at the wrong items.

Seriously i dont know if buying at system pressure regulator at 50 bucks is worth the money.

My Fd number is 0438100097 i 've gotta get a rebuilt from the like like germanstar, pelican does not stock the ROW.

[GaryR]

Originally Posted by john walker's workshop

did you check to see if the screen in the WUR is clean yet, as i suggested earlier? a blocked screen (particle matter/rust) can cause your problem.

Are you not trying what John said (twice!) for some reason?? He is about the most knowledgeable, experienced person here!!

[Peter Seow]

Forgot to mention that lean out condition at high reevs is the same when cold or hot so it seems the WUR is not the most likely culprit.

At least it's nice working on the car you know, and have the all the history about. Used to street race, participate in rallies though rough mud condition, tracks days and yes was used in shifting my house in this carried most of my stuffs lees the big furnitures.

I crossing my finger but if the returns lines from the fd is not the culprit its probably the fd i will bench test, i ve even accumuate a set of new injectors. for the bench test i and going to use the injectors from an CIS w126 280 se going to use a merc fuel pump as well i domnt think i can replicate the pressure accurate but at least i can get a rough idea.

[Peter Seow]

Originally Posted by GaryR

Are you not trying what John said (twice!) for some reason?? He is about the most knowledgeable, experienced person here!!

Forgot to mention i did that when unplugged all the joins to the WUR when i was testing the control pressure. I used an air gun to blow it duh nothing.... i wished the problem was that.

Now it seems isolate that the FD or the return line from the FD is having a problem as there is some containment here.

I am using the reading from Ben watson's how to tune and modify bosch fuel injection. No thinking i bought the book ten years ago... I think my car problem were minor ten years ago...its major now.

[boyt911sc]

Originally Posted by GaryR

Are you not trying what John said (twice!) for some reason?? He is about the most knowledgeable, experienced person here!!

Peter,

Do you know what your are looking for? This is basic CIS troubleshooting!!!! JW has given you the simple test. I illustrated to you other places to locate the restriction. Are you asking for help or want to do it your way? I'm no expert, but this is a 10 min. work to determine where the problem is and JW could surely do it faster. He's the guru!!!

For the control pressure to equalize the system pressure is a sure sign of flow restriction!!!! The question is where does this occur? It could happen @ FD return, @WUR return, or @ return line to the tank. Which includes the line from tank to the t-connection near the engine. Good luck.

Tony

[john walker's workshop]

did you determine that the FD pressure valve is not sticking yet? got to remove it to find out. you should be able to extract it with a small magnet stick.

[Peter Seow]

Originally Posted by boyt911sc

Peter,

Do you know what your are looking for? This is basic CIS troubleshooting!!!! JW has given you the simple test. I illustrated to you other places to locate the restriction. Are you asking for help or want to do it your way? I'm no expert, but this is a 10 min. work to determine where the problem is and JW could surely do it faster. He's the guru!!!

For the control pressure to equalize the system pressure is a sure sign of flow restriction!!!! The question is where does this occur? It could happen @ FD return, @WUR return, or @ return line to the tank. Which includes the line from tank to the t-connection near the engine. Good luck.

Tony

Tony Correct, So far,

I am left with the where the restriction takes places,

having eliminated the return line to the tank,

I've got two place to test the return line from FD- not done yet and that T connection

[Peter Seow]

Originally Posted by john walker's workshop

did you determine that the FD pressure valve is not sticking yet? got to remove it to find out. you should be able to extract it with a small magnet stick.

No yet planning to test the return line from FD and the pressure valve

[Peter Seow]

Originally Posted by Peter Seow

No yet planning to test the return line from FD and the pressure valve

Took out FD. Tested return lines from FD and WUR, nothing again all cleared now i am going to bench test my FD.

Will do it after dinner tonight...

AT the same time i just enlarged a hole in the door panel to fit my 993 door mirror switch will be wiring up my 993 door mirror.

Thank you for all the help,
Thanks to John, tboy and everyone out there to help trouble shoot it... am now left with that FD...

[boyt911sc]

Originally Posted by Peter Seow

Tony Correct, So far,

I am left with the where the restriction takes places,

having eliminated the return line to the tank,

I've got two place to test the return line from FD- not done yet and that T connection

Peter,

Based from the information above, that you have eliminated the return line to the tank, does not make sense to me unless you have completely detached the return line connection to the gas tank and did a pressure test!!!!!! If you have done it (complete return line disconnected) and high pressure did not change, proceed to the next fitting toward the engine. The next connection is located just above the transmission support (provided you have OEM fuel lines), followed by the fitting at the TEE (return line).

What tests have you done so far to eliminate the fuel return to the tanK? Keep us posted.

Tony

[boyt911sc]

Originally Posted by Peter Seow

Took out FD. Tested return lines from FD and WUR, nothing again all cleared now i am going to bench test my FD.

Will do it after dinner tonight...

AT the same time i just enlarged a hole in the door panel to fit my 993 door mirror switch will be wiring up my 993 door mirror.

Thank you for all the help,
Thanks to John, tboy and everyone out there to help trouble shoot it... am now left with that FD...

Peter,

I hope you are correct!!!!!! But I have not seen any test that confirms the return line to the tank is not restricting the flow of fuel!!!!!!! The return line per se is not just one piece of fuel from FD and WUR. It includes also the long fuel line that goes thru the tunnel. Detaching the return line involves partial draining of the fuel tank and removal of the line. Which at this point is not obvious to me that you have done so far!!!! If you did, I have nothing to contribute.

Tony