308QV K-Jet testing, help!

I'm trying to figure out why my 308QV doesn't run well when cold. I checked the AAV. I checked all the electrical connections. I replaced the cold start injector. Now I've moved on to pressure testing the injection system. I have no experience at all testing a Bosch K-Jet system, but I dove right in to see what I could see...

I hooked up a pressure tester gauge and shutoff valve between the fuel distributor and the Warmup Regulator and the readings I get are a bit confusing to me. The control pressures (read with the shutoff valve open, allowing gas into the WUR) read 51psi (3.5 bar) with the engine both warm and cold (sitting overnight). The system pressure (with shutoff valve closed, bypassing the WUR) reads 15psi (1 bar).

Now, I'm lead to believe that the cold control pressure should by around 1 bar and the warm control pressure should be around 3.5 bar. Since both readings are a 3.5 bar, that would make me think the WUR is broken. But, shouldn't also the system pressure constantly be about 4.5-5 bar? Why the heck would it be all the way down at 1 bar?

Can anybody give me some direction here?

 

Sounds to me like you have the gauge hooked up backwards. You seem to be reading control pressure but not system pressure. The leg of the "T" with the valve should hook to the WUR. It sounds like your WUR is bad. If you call me I can go over all the tests you need to do.

Larry
251-929-3771

 

Spot on Larry, I do indeed have it on backward! I'll switch it around and try again. And thanks for the offer to help over the phone, I may just take you up on that!

 

Ok, that seems to make a lot more sense. With the guage/valve turned around this morning I now get the following readings:

cold control pressure: 3 bar
warm control pressure: 3.5 bar
system pressure: 5 bar
rest pressure: 3 bar (for at least 20 minutes)

So, I'm going to assume the WUR is broken, since cold control pressure should be down around 1 bar, yes?

 

Look for a plugged up screen on the inlet side of the WUR. Blow air through it backwards and recheck the pressures

Dave

 

Jeremy here are the results of the FPT that I took years ago. Just thought you might be interested. Why did you replace the CSI? Did you check the TTS to make sure it works correctly?

Cold Control = 26 PSI
Warm Control = 47 PSI
System Pressure = 72 PSI
Rest Pressure = 42 PSI (after 20 mins.)

 

(For anybody listening in, 308GTS used to own my car)

No, I didn't actually test the TTS. But the CSI didn't work even when I put an external 12VDC supply on it.

So you were getting 1.7 bar cold, that sounds a lot better than what it's doing now. Did it have the cold start issue when you measured that?

 

What is it doing now? Yes it used to start right up. Is the idle just not coming up or is it starting then stalling immediately?

 

It stalls immediately on cold start up, about two to five times. Then it runs, but really badly until the engine warms up a bit. After that, it runs fine. Before I replaced the CSI it also had to crank like 10-15 seconds before it would even catch the first time. BTW, what were you checking that made you test the pressure?

 

I always check it to get a baseline for a car. The bosch specs are good but I like to have a baseline for each car so if it acts up I will know exactly what the fuel pressures are. I had another K-Jet equipped car that was slightly out of spec and ran like a top so I was glad I took the fp's. When it had a fuel problem many thought it was a bad WUR due to it being slightly out of spec but it wasn't. If the CCP (cold control pressure) is too high it will cause exactly what you are experiencing. The pressure is too high causing the plunger in the FD to not come up as high as it should causing too lean of a mixture for it to start up and run properly. Assuming you checked the other components it very well could be a WUR.
I think this is the Bosch part # for the WUR on that car. 0 438 140 132
I think that fits 328s also.

 

Listen to larry or Dave. Larry routinely rebuilds CSI stuff.

 

No difference. So I've ordered a rebuilt WUR from specialtauto.com, which means my car is off the road for a week or so

 

Sure sounds like you've found it.

Altho, I"m puzzled why the CSI wouldn't spray, especially with that kind of system pressure.

 

It wouldn't even spray when I hooked it up to an external 12VDC source, so I think it was just completely clogged or the internal wiring was broken. I have a feeling though that it wasn't really the source of my trouble, and we just stumbled upon that issue. From what I've been reading I'm not sure it really does a heck of a lot of spraying anyway above 60 degrees F or so because the TTS wouldn't be closed at temps above that, even on a cold engine.