83 Fuel System Rebuild

[amarino]

The 2 books I linked above might have something.

Can also check out the DIY/FAQ thread under "The CIS Pressure Test":
https://www.bimmerforums.com/forum/s...7#post15904137

[jbowen944]

Amarino, thanks. Been hectic here wasn’t able to find that while I’m pulling parts. Should have some exciting news for E21 enthusiasts coming in the next month or two.

[cgifool]

To test your fuel pressures, connect the CIS pressure gauge setup between the WUR and center port of the fuel distributor.

That is, disconnect the fuel line that runs between WUR and the middle of the fuel distributor.

On your gauges, there will be T of hoses, with the gauge on one leg and a shutoff valve on the other, with the gauge in the middle.

Connect the shutoff valve end to the port in the middle of top of the fuel distributor, and the other end to the WUR.

Disconnect the electrical connector from the WUR, jumper the fuel pump relay, and turn on the ignition.

With the gauge's shutoff valve OPEN, you are measuring CONTROL pressure. With the shutoff valve CLOSED, you are measuring SYSTEM pressure.

This page shows better description and photos, different kind of car, same setup:

http://cleanflametrap.com/kjetGauge.htm

[jbowen944]

Built a CIS pressure tester over the weekend, ran the numbers. at 56F, Cold Control Pressure was 38psi, System Pressure was 68psi, Warm Control Pressure was 50psi. System passed the leak test, staying above 22psi for over a few hours. From what I'm reading, my Cold Control Pressure is fairly high. I've cleaned the WUR, but I'm going to pop it out and run the body through the ultrasonic to make sure it's clean through and through. I'm also going to check my lines for blockages post WUR. Any ideas on what's up? Can high control pressure limit spray from the cold start injector? Attached is a picture of my tester, from when I was running it earlier today.

IMG_1387.jpg

[GDAus]

Built a CIS pressure tester over the weekend, ran the numbers. at 56F, Cold Control Pressure was 38psi, System Pressure was 68psi, Warm Control Pressure was 50psi. System passed the leak test, staying above 22psi for over a few hours. From what I'm reading, my Cold Control Pressure is fairly high. I've cleaned the WUR, but I'm going to pop it out and run the body through the ultrasonic to make sure it's clean through and through. I'm also going to check my lines for blockages post WUR. Any ideas on what's up? Can high control pressure limit spray from the cold start injector? Attached is a picture of my tester, from when I was running it earlier today.

Hi ..

umm ... No ... the CSI runs off the system pressure.

What is happening is that your higher cold control pressure is preventing the metering plate in the Air Flow Meter from rising far enough to enrich the mixture for starting. At 56 ⁰F your Cold CP should be in the range of about 9~15 psi. Also, the Aux Air Valve works with the WUR to allow extra air for the extra fuel. Of course every engine is a little different because of tolerances and usual wear and tear. So the chart below shows a range of acceptable Cold CPs and there is an adjustment nut on the AAV to allow a bit of tuning to match the 2 together.

I'd be checking the filter screen in the line from the FD to the WUR. I had that problem with mine ... it was partly blocked with glazed fuel and to the naked eye just looked wet with fuel. I was only when i got a pressure gauge set that I found my Cold CP was way high and a closer look under 60x magnification that it became obvious what the problem was.

Hope this helps

Cheers

[jbowen944]

Scrubbed the screen on my WUR, took cold control pressure down to 35 at 70F. My cold start injector is still not spraying though. I hear the solenoid click, but no fuel comes out. Anyone have any ideas on what to check? I'll have all day tomorrow to tackle the issue, but I'm low on time to research causes to suss out. All help is welcome, thank you all!

[epmedia]

Scrubbed the screen on my WUR, took cold control pressure down to 35 at 70F. My cold start injector is still not spraying though. I hear the solenoid click, but no fuel comes out. Anyone have any ideas on what to check? I'll have all day tomorrow to tackle the issue, but I'm low on time to research causes to suss out. All help is welcome, thank you all!

Have you tried cleaning the inlet filter on the cold start injector yet? I once tapped the inlet onto a piece of plywood, saw debris come out. Then sprayed carb cleaner to the inlet and tapped repeated several more times. Worked good after that.

A note on the WUR inlet screen - there's probably multi-stage felt filters under the metal screen that could be mucked up too.

[jbowen944]

I ran the WUR body through the ultrasonic, and flushed it with carb cleaner, got it to where I could blow through it with minimal resistance. I flushed my cold start with carb cleaner, but I’ll pull it and try again.

[GDAus]

Scrubbed the screen on my WUR, took cold control pressure down to 35 at 70F. My cold start injector is still not spraying though. I hear the solenoid click, but no fuel comes out. Anyone have any ideas on what to check? I'll have all day tomorrow to tackle the issue, but I'm low on time to research causes to suss out. All help is welcome, thank you all!

Hmm .. still way to high ... at 70^o F the cold CP should be in the range of about 13~19 psi.

I should have mentioned a bit about the checking procedure. It's a bit tricky to check the pressures with the engine running. As soon as the ignition is turned on, if the electrical connector to the WUR is plugged in, the bimetallic strip inside the WUR that changes the pressure starts to heat up and change the pressure. Also the engine needs to be off for about 6 hours to ensure it is at ambient temperature for checking purposes.

So, when I check Cold CP on mine ....
I leave it overnight with a thermometer sitting on the WUR so everything is at a known stable temperature and use the table to see what pressure the Cold CP should be.
Unplug the electrical connector to the WUR
Check the pressure with the engine stopped and running the fuel pumps by removing the fuel pump relay and using either a bypass connection with the ignition on or a direct connection to battery +ve and the GREEN/Black terminal (87) in the relay base. This stops any changes from the heat of the engine or the internal heater in the WUR so the cold CP can be adjusted more accurately.
After checking/setting, replace Fuel Pump Relay and electrical connector to WUR, start engine .... check that pressure starts to rise within a few minutes.


Have you had your WUR fully apart ? Not sure if you have it apart and able to blow through the valve?

If you take it apart and without the internal springs acting on the valve that controls the control pressure .. you should be able to blow air easily through the 2 fuel line ports from one to the other. It's possible it might have some gunge inside the valve itself.

For cleaning the fuel injectors etc I use Liqui-Moly Diesel Purge Fuel system cleaner. Not in the fuel tank ... just as a cleaning agent!

Back when I first got my E21, the injectors were pretty clogged and I was wary of using anything that might damage the internal seals on them. So looking for some info on cleaning them I found a site from a company that services Mercedes-Benz Diesels and K-Jet equipped cars and they did a test on soaking badly clogged injectors in it for a couple of weeks and then cut open some of the injectors to see if it had harmed the seals No visible signs of it causing and harm. I thought that was a pretty good test and I have used the Liqui-Moly on my injectors a few times and to wash out my WUR with no problems.

Actually adjusting the Cps can be tedious and very frustrating because it involves gently hammering the cylindrical valve body (the bit where the fuel lines attach) in or out plus also if necessary moving the steel post (small diameter depression next to the valve body) that has the internal Bi-metallic strip attached to it that controls the Cold CP in and out too.

For example .. if yours has no obstructions to the control valve then it means the post needs to be moved inwards to lower the cold CP which can be done from outside the WUR.

Somewhere I have some graphics to show what I mean, but I can't find them at the moment. When I have a chance to find them I will post again and go through the adjustment process in a bit more detail if you need it.

As to your CSI problem ...

+1 to what Robert (epmedia) has said.

The CSI can get clogged just like the other fuel injectors and the first thing I did was exactly this when I found mine was spraying erractically. You can also hook up 12 volts to the CSI to open it and back flush the injector too.

Cheers

[jbowen944]

GDAus, I've fully disassembled the WUR for cleaning. I've been through a few of the workshop manuals, and I promise I'm testing it right. I always unplug the WUR plug, and currently the car can't start due to my cold start injector issues. My fuel pump is jumpered for testing, and my cold testings are taken with a cold engine, Warm pressure readings are taken with a plugged in WUR, as I can't get a reading with engine temp, due to the no start issue.

[jbowen944]

I'm going to pull my fuel line from the cold start injector and see if it's delivering fuel tomorrow, along with shimming the bi-metal strip in the WUR instead of trying to knock it. I'll post results.

[GDAus]

I'm going to pull my fuel line from the cold start injector and see if it's delivering fuel tomorrow, along with shimming the bi-metal strip in the WUR instead of trying to knock it. I'll post results.

Hi ....

I threw in the question about the WUR in case you needed more info on stripping it down ... I've found some good articles over the years about that if you needed them. Sometimes it's hard to figure out what someone has or hasn't done ... so I do over explain things at times, just to try and cover all the bases and help anyone who reads the posts in the future. So I will add this little bit extra for anyone wanting to adjust their WUR.

Doing adjustments to the WUR on the car:
It involves using a drift and a hammer to move the valve body and/or the post into the WUR body. It does sound a bit bonkers to do this, but this is how the WUR is calibrated in the factory to give the right pressures.
Use the technique in my previous post to check the Cold pressure as the adjustment is taking place

Any adjustments need to be made in lots of small steps ... because if you drive either the valve body or the post TOO FAR into the WUR casing ... then you have to remove the WUR, pull it apart to be able to push the bit(s) back out again, re-assemble it, put it back on the engine and try again. I managed to do this on my first attempt and it is definitely one of those OHHH NO moments but it's not the end of the world

If you have the WUR out of the car .... it's a good idea to mark the valve body with a scribe line to show its original position and measure how far down the hole the post is, to give a reset point if you mess up. When I stuffed up the first time I tried to adjust my WUR, having done this made it a lot less hassle than it could of been.

I used an old bit of 3/8 inch rod I had lying around .. ground the tip down to fit in the hole at the top of the post and long enough to reach down to the WUR so I could hammer on it above all the other stuff that live down there. I used one of the smallest hammers I have and a tapping motion from the wrist to find the right amount of force that will cause a change in the control pressure your trying to adjust. A little bit of movement can give a big change of pressure.

Changing one the of the pressures may change the other pressure a bit too ... so a bit of tweaking between the 2 adjustments may be needed.

If you need to raise the Cold CP or lower the Warm CP .. You will first have to open up the WUR and tap the post or the valve body a bit further out to be able to adjust them inwards to get the correct settings.

Cheers again