280i Fuel Pressure Issues

[Grady]

Starting a new thread as I've moved along some. Hopefully I'm on a good path but not confident.:

Goal: Checking/adjusting fuel pressure(s) (86 USA 280i) for driveablity.

Backstory:
Had to park the car for 3-4 years to wait out emission testing; ran it on a monthly basis. Ran fine when parked. Everything that has been done has been to replace "tune-up" type parts, no major surgery. Just trying to get on the road as time/weather allows (~50K miles). Accumulator, fuel filter, plugs, cap and rotor, wires and amplifier replaced; it has fuel. It drives/runs but not well.

Testing with a good quality CIS specific hose set and gauge.

Step #1
Bypassing the the USA safety module: Easy - Left everything alone and ran a long jumper from the battery to the positive on the fuel pump (usual fire/safety warnings), Unhooked from the battery when not actively testing.
Unplugged the wiring 4 connectors to the cold start, WUR, etc. per manual.

Step #2
Tested pressure between filter and metering head: 69 PSI / 4.75 Bar (This appears to be ~w/in spec)

Step #3
Substituted the fuel line between metering head (top center) and WUR (other end of the same hose, left side hose) with test gauge (cut off valve on the WUR side)

Step #4
Tested with valve closed ~69 PSI / 4.75 Bar and then open ~66 PSI / 4.5 Bar (so system pressure is almost the same as control pressure) ???

Bonus
Holding pressure, so the accumulator is doing its job.

Does this look ok?



Per my manual, the control pressures (at 66F/20C) should be between 0.6 and 1.0 bar so clearly something is FUBAR.

Looks like I may have a "wide open" WUR. I have never removed the WUR so it is soaking.

Thanks, Grady

Edited by Grady on Sunday 2nd February 19:10

[KelvinatorNZ]

I'll be posting a three part test/tune saga on KJet tonight after work, will reply here when it's ready.

The gauge looks right. Your system pressure is low and your control pressure is high. My bet is on a blocked WUR mesh.

[adam quantrill]

Don't want to hijack the thread but what time limit were you waiting for on emissions Grady? As a matter of interest.

[KelvinatorNZ]

Finally done. Here is the trilogy. Hope it helps


Part 1 https://www.tasteslikepetrol.net/2020/02/bosch-k-j...
Part 2 https://www.tasteslikepetrol.net/2020/02/bosch-k-j...
Part 3 https://www.tasteslikepetrol.net/2020/02/bosch-k-j...

[Grady]

FYI - Sunday I ran the car up to operating temperature and the control pressure didn't change.

And I tried to remove the WUR but the two allen bolts were not moving. I'm soaking them this week and will try again next weekend with a little tapping/heat/battery impact driver. Didn't help I couldn't find by 6mm allen socket. They are well protected by a U shaped shelter of steel (US emissions addition).

adam quantrill said:

Don't want to hijack the thread but what time limit were you waiting for on emissions Grady? As a matter of interest.

The greater Houston area is a recognized high pollution area because of all our oil/gas/chemical industry. So the old standard was an annual tailpipe sniffing OBD1 type test (rolling road?) until the car was 26 years past its manufacturing date. Then it is just an annual safety-only inspection which is much less intense that an MOT. Basically, horns lights.

There were some exemptions, in my case under 5K miles per year, but it was a huge pain to get processed and they always found something else wrong. One year it was the red TVR logo/band on my windshield which had always passed before. I agreed to scrape off on the spot but they made me schedule a 2nd appointment a month later. They didn't want to make it easy.

But I just took my chipped and supercharged OBD1 E-38 in (which always fails on hydrocarbons) and learned that Texas did away with the OBD1 testing last year (I guess because all cars are either ~25 years old or OBD2 compliant.) BTW – each state sets its own inspections standards in concert with the Federal EPA depending on local air quality.

KelvinatorNZ said:

Here is the trilogy. Hope it helps

Thanks, I keep rereading your other Tastes like Petrol postings as well as a couple of other I’ve found. Beginning to get my head around this, I hope!

Edited by Grady on Monday 3rd February 18:59

[KelvinatorNZ]

The two mounting bolts are a pain. Both of mine were pretty crusty and one broke on removal. Still haven't extracted the remains, but it acts like a dowel now and the one remaining bolt is slathered in copper grease to aid removal in future.

The one thing about your WUR is that its not "wide open", its the opposite, it's blocked or set too high. If it were wide open you would have very little pressure on the gauge as its the resistance through the WUR that shows as a higher pressure on the gauge. The control pressure should never exceed the system pressure, hence why they are similar. A pressure that high would indicate you are running very lean at all times; probably ok when warm (although still leaner than it should be) but cold would be a dog.

[adam quantrill]

Great stuff Kelvin - have added to the FAQ.

[Grady]

Yes, the Trilogy is a great resource and very well written. I'll be doing a practical this weekend. Please make sure the pictures are securely saved too. Grady

[KelvinatorNZ]

Thanks. I look forward to seeing how you get on with your testing.

[Grady]

The good new is the WUR came off cleanly and disassembled with little fuss. I couldn't find the diaphragm until I realized to was stuck to the cover.

The mesh looked gunked up. How do you spray through the mesh directly from the inside since the inlet is behind the circular part that the diaphragm/cover bolts to? Anyway, I cleaned it and now if I spray into the mesh, it drains through.

In the first test, (with no bottom on the WUR), I showed 0.7 BAR but by pressing on the cup/diaphragm, I could move the pressure came up to ~4.5 BAR. Probably could have gotten it higher.

I attached the bottom of the WUR, and got the same 69 PSI / 4.75 BAR system and may a 1 PSI less on control. I tapped down on the cold pin (previously tapped up a stoke more than flush) and nothing changed, I've driven the pin down a measured 1/4 inch (about twice as far as it was when I first removed the WUR I think) with no change is PSI / BAR. I stopped as I was getting afraid I'd pop it in.

How far did you sink the cold pin before you saw results on the gauge? Or how far is it below the surface now? Thanks

[KelvinatorNZ]

Grady said:

The good new is the WUR came off cleanly and disassembled with little fuss. I couldn't find the diaphragm until I realized to was stuck to the cover.

The mesh looked gunked up. How do you spray through the mesh directly from the inside since the inlet is behind the circular part that the diaphragm/cover bolts to? Anyway, I cleaned it and now if I spray into the mesh, it drains through.

In the first test, (with no bottom on the WUR), I showed 0.7 BAR but by pressing on the cup/diaphragm, I could move the pressure came up to ~4.5 BAR. Probably could have gotten it higher.

I attached the bottom of the WUR, and got the same 69 PSI / 4.75 BAR system and may a 1 PSI less on control. I tapped down on the cold pin (previously tapped up a stoke more than flush) and nothing changed, I've driven the pin down a measured 1/4 inch (about twice as far as it was when I first removed the WUR I think) with no change is PSI / BAR. I stopped as I was getting afraid I'd pop it in.

How far did you sink the cold pin before you saw results on the gauge? Or how far is it below the surface now? Thanks

I used brake clean with one of those little straws attached to clean the mesh. If you look at the underside of the WUR with diaphragm removed there are two holes. One for the inlet, and one for the outlet. I cant recall which is which, but I cleaned it upside down over a sheet of paper and it was shocking what came out of it. I used the straw to force the spray through the hole.

The first test sounds good, those are the pressures you want.

I still believe your system pressure is low. It should be about 5BAR, you need to sort that before continuing. 4.7BAR is the MINIMUM system pressure in the workshop manual. 5.1BAR is recommended.

Test two is the top and bottom assembled without the bimetalic strip, which you should see 3.5BAR or higher. Because the strip is removed (which is what the pin acts on) you will not see any changes moving the pin here. You need to fully reassemble with the pin high, and then use the pin to lower the cold control pressure. With the WUR assembled you should see changes pretty quickly when you start to tap down the pin.

[Grady]

KelvinatorNZ said:

If you look at the underside of the WUR with diaphragm removed there are two holes. One for the inlet, and one for the outlet.

Once I removed the diaphragm, I still had the circular piece with 4 small bolt holes and the O-ring on top. It blocks direct access to the inlet and outlet from the inside so I couldn't get to the screen directly, even with the straw. Does that further dissemble? Looks like the entire part could be pressed out of the upper housing.

Anyway, shims and O-rings ordered for the system pressure adjuster. Not sure when they are coming in.

[KelvinatorNZ]

Grady said:

Once I removed the diaphragm, I still had the circular piece with 4 small bolt holes and the O-ring on top. It blocks direct access to the inlet and outlet from the inside so I couldn't get to the screen directly, even with the straw. Does that further dissemble? Looks like the entire part could be pressed out of the upper housing.

Anyway, shims and O-rings ordered for the system pressure adjuster. Not sure when they are coming in.

Under the diaphragm should look like this, with the recess for the o-ring


The two holes for the inlet and outlet are the one dead center, and the dark one directly below the center hole, within the o-ring. IIRC the one off center is the one you need to clean through. I used the straw to force brake clean through that hole under pressure.

If you struggle to clean it like that, it would be worth getting hold of a small ultrasonic cleaner and using that to clean the top half.

You can completely press out the part, but there is no benefit to this as its all sealed. You can tap that whole pressed in section up or down to adjust warm pressures if needed (set per Step 5 of my tuning)

[Grady]

I found some time this weekend and K-Jet parts came in from Delorean Go.

First, I replaced the O-ring on the pressure switch - No change.

Then, I added the thickest shim in the set I got (there were none installed) - That bumped the system pressure to 5.4 Bar.

Then, I tested the pseudo-warm pressure and got 2.75 Bar.

So I drilled off the copper cap and tapped the interior pin in - bumped 2.75 Bar to 4 Bar.

Making progress I was thinking...

Reassembled and the pressure went back to ~5 Bar. Disassembled and all looked OK, reassembled, pressure at ~5 Bar.

Tapping on the cold pin didn't do anything. Also the the engine is now barely running, needing constant throttle action to try to keep it running.

Gave up for today.

Edited by Grady on Monday 24th February 00:16

[KelvinatorNZ]

None of the testing and config should be done with the engine running until you're at the point of tuning the warm pressures. Trigger the pump manually with the engine off.

System pressure is a bit high, maybe try a different set of shims to bring it closer to 5BAR. I'm surprised there were no shims at all before, that's not normal.

With the system pressure changed you need to start from Step 1 again as it throws everything out.

Unless the WUR is FULLY assembled, with heater strip etc, the cold pressure pin DOES NOTHING, and will do nothing. This is normal as the cold pin acts on the heater strip. Without the heater strip, it has nothing to move.

When you get a chance, please let me know what pressures you get for each step, it will help identify where the issue lies.

System (5Bar) -
Step 1 - Full flow no resistance (0.5BAR raising to over 4.5BAR when diaphragm pressed) -
Step 3 - Pseudo Warm (3.5BAR or HIGHER) -
Step 4 - Cold Cotnrol (0.5BAR - 1BAR depending on temp) -
Step 5 - Warm Control (3BAR) -

I know how frustrating this is, I've been there, but the reward of a working KJet that you fixed yourself, is well worth it. Keep at it.

[Grady]

Back at it...

First - I adjusted the system pressure to 73 PSI - 5 BAR. (engine off ) It turns out there was a shim installed. Stuck on and I didn't see it before.
Step 1 - 9 PSI to 70 PSI (.6 BAR to 4.7 BAR)
Step 3 - 4.5 BAR
Step 4 - (Cold Control) Here is where it got off the rails. I reassembled the heater bar, hooked up the hoses and tapped the pin down. And eventually the pressure started dropping. Unfortunately I tapped once too much and the pressure dropped to 10 PSI. (0.6 BAR) My goal was 13-19 PSI based on the ambient off 77F or 25C so I took it apart again.

But as I looked at it, I got to thinking that I had installed the heater bar upside down. IIRC, the writing was on the visible side when I disassembled it. So I reassembled it, but driving the pin down had no effect and ultimately drove the pin out with no effect on the cold pressure.

This is what it looks like now. From the bend at the Mexican hat end does it look correct? It seems to fit properly this way but since it was actually adjustable with the other side up, I may be miss-remembering.

Edited by Grady on Monday 16th March 00:05

[KelvinatorNZ]

It's looking better, you're getting close!

But yes the heater and maxican hat are wrong. Heater is upside down, and Mexican hat should rest on the other side of the heater strip (the springs in the base rest in the Mexican hat when assembled). The pin under that hat should pass through the strip.

You can see mine here. The hat has fallen off the strip. It's a balancing game to reassemble it lol.

[Grady]

OK, so next weekend, I'll flip the heater over. Which should give me pressure control. Stand by please.

[Grady]

Well, with the Mexican hat on properly I got good pressures. I then removed the pressure sensor threaded ends and reinstalled the banjo fittings on the on the WUR and metering head... and got a large fuel leak at the WUR. Dried everything off and changed out the copper washers and it leaked in a different direction. Another set of new washers just changed the direction. Gave up for the night in disgust.

[KelvinatorNZ]

I had lots of issues with leaks at the WUR. Check the surfaces of the banjo and WUR are clean and smooth, and only use new copper washers of the M8x12x1mm (Fuel Dist/WUR) and M10x14x1mm (WUR) sizes. There is a torque setting for them too, it's quite low but I don't have it on me right now. I will update later with it.

Edit. 5-8NM for the small ones, and 11-15NM for the big one.

Edited by KelvinatorNZ on Friday 27th March 11:37