CIS pressure test, question

[npresley]

So I've been checking parts, I do not believe I have a separate check valve at the fuel pump. I removed the fuel line from the bottom of the accumulator, and pinched it the line. The accumulator drained, and I let it sit over night and started the engine the next day. I let the engine run for a few minutes. The fuel pressure read about 2.1 bar, while engine running. Shut the engine off and watched the accumulator - nothing came out. I looked around and found the thermal valve was not connected by vacuum to anything. Its ports had vacuum caps, and the port on the WUR that goes to the thermo valve was capped. Manifold boots, ignition components, injector orings, fuel pump, fuel filter, & accumulator are roughly 3 yrs old with about 5000 miles on them.

[T77911S]

2.1 is low for WCP not matter. that could be OK for CCP.

make sure you have 12v going to the WUR.

there should be 2 ports on the WUR. one is a vent and one is the vacuum port. i think it is the top one that is vacuum. just connect it to manifold vacuum.

[npresley]

Top port is connected to a port on the throttle body, but the side port is capped. 1.5 bar is a little low for CCP, according to the little factory spec book. I'll check the voltage at the WUR electrical connection next.

[Vereeken]

The top port should be atmosphere (try it you should not feel any suction at any rpms).

The side port is vacuum. This vacuum does not change much through the rev range, but you should feel it suck distinctly. Apologies for the choice of words. The vacuum for this port should come from the back of the TB possible T-ed from the decel valve if you have that.

Ofcourse there is a WUR in existence that changes the above outlay (made by a german engineer that had a bad marriage).

Could it be that you have a 77 with a Bosch 089 WUR installed. Like T77 says. 2.1 is too low. I think you have CCP and nothing else. Most likely because of no 12v to WUR.

The WCP could rise if the engine is really hot and you have engine heat that rubs off on the WUR but even then it needs the 12V source all the time to stay stabil.

Michel

[T77911S]

the 77 had the vac port on top. it was moved to the side for the 78-79.
if the diaphragm in the WUR is good, and the WUR is connected to the correct port on the TB (as said above), then when you remove the hose, the pressure should go down.

did the pressure rise to 2.1? i did not see where you really had some good readings when the engine is cold to warmed up.

1.5 CCP being too low depends on if the vacuum circuit is working or not.
this is what i like about the 77-79 CIS systems. the very low CCP. it helps with backfiring when you first start it.

here is what we need to be clear:
CCP with engine not running, no power to the WUR
if you have a hand vac pump (very nice to have) pull a vac on the WUR CCP and see if it changes.
start the engine with out power to the WUR. does the CP rise after about 30 seconds.
connect power to the WUR does CP rise and to what value?
do you have 12v to the WUR?

the goal is
CCP without vac
CCP with vac
WCP without vac
WCP with vac.

you dont need the TTV for driving or starting, but you do need the vacuum circuit to work. it makes the car drivable. i explain it like the accelerator pump on carbs. it gives a little extra fuel when you give it gas and it makes it richer at WOT.

[npresley]

12.6 volts at plug for WZuR when started

[npresley]

CCP with engine not running, no power to the WUR1.6 bar
if you have a hand vac pump (very nice to have) pull a vac on the WUR CCP and see if it changes. pressure lowers to 1.1 bar
start the engine with out power to the WUR. does the CP rise after about 30 seconds.at start, 2 bar, no change in 30 secs
connect power to the WUR does CP rise and to what value? no not immediately, after 30 sec rises to 2.3 bar
do you have 12v to the WUR? 12.6V

[Vereeken]

"start the engine with out power to the WUR. does the CP rise after about 30 seconds.at start, 2 bar, no change in 30 secs"

I think you did that test immediately after the 1st, correct?. Therefor the thermal valve was already open and vacuum applied to the WUR. The 12V at the Thermal valve should also be disconnected when you do your first tests.

What was the outside temperature at the moment of your test. I have a couple of thermal valves and the longest hold-off of vacuum by a thermal valve I have seen is 50 seconds at -5degrees celcius. It is 20 degrees celcius outside in Belgium and the Thermal valve holds off vacuum for not more then 10 seconds at this point in time.

But regardless all this points to a WUR that does most correct. Only the WCP is low.

But to be sure you need to do one more test , we need to have the WCP after 5 minutes of 12.x Volt applied to the WUR to be sure. Best is to let the engine run. If you do it only by jumping the fuel pump you will not get 12.x at the WUR and it really needs that to be accurate.

The best I can think off now is a defective bi-metal.

Lets see what TT has to say.

Ah yes, after this 5 minutes we also need a cool off test with 30 sec intervals for 5 minutes.
Michel

[npresley]

The pressure bleeds off to 0 after about 30 seconds, once the engine is shut off. The thermal valve is not connected to anything by vacuum. I want to recheck the voltage. I started thinking about how sometimes a wire will connect and work at a certain position and then you move it, and you don't have a good connection. I'll check and report back. Is it agreed that I need to replace the accumulator, or hold off and do some more tests?

[npresley]

I tested the WUR electrical connector again. It didn't matter if I slung the thing around over my head, it still read 12.6V. Something interesting though, the electrical connector on the front side of the throttle body (towards front of car), that controls if the fuel pumps runs when the key is on. If that is connected, I do not get any voltage at the WUR until the engine is started. I then read 12.6V at the WUR electrical connection. If the fuel safety switch is disconnected, so that the fuel pump runs whenever the key is on, I read 10.8V at the WUR. I then start the engine and read 12.6V at WUR electrical connection.

[Vereeken]

Well that bleed off sure is fast. Indeed common knowledge says fuel accumulator.

Can the Fuel Accumulator explain the low Warm CP? I am not sure.

The voltage issue is a none issue in my opinion.

However, when you say 12.6V is that with engine running? Or just jumpering the fuel relay? I would have hoped to see 12.9/13.0 at 1.000rpm.

Does the voltage rise slightly with RPM?

Michel

[timmy2]

Accumulator, everything else seems fairly normal.

[T77911S]

your pressures are too low. you may get away with making the WUR adjustable. WCP with the engine running should be 3.4bar.

start with WCP and set it first. then the next day set the CCP. you can do the CCP with the engine off and power removed from the WUR.

there are a lot of threads about making it adjustable, or just buy a new one.
when you make it adjustable, you still may not be able to obtain correct CCP and WCP. you will be able to set it for one or the other but the WUR may no longer be able to go from CCP to WCP, or, you can set it for WCP but it will not go low enough for CCP.

[npresley]

Thanks everyone. I hope more people will read this thread and get some good information/insight.

[npresley]

Thanks everyone. I hope more people will read this thread and get some good information/insight.

Vereeken: not jumpering the fuel relay, didn't rev engine and watch voltage @ WUR plug.

[ossiblue]

Originally Posted by npresley

So I've been checking parts, I do not believe I have a separate check valve at the fuel pump. I removed the fuel line from the bottom of the accumulator, and pinched it the line. The accumulator drained, and I let it sit over night and started the engine the next day. I let the engine run for a few minutes. The fuel pressure read about 2.1 bar, while engine running. Shut the engine off and watched the accumulator - nothing came out.

If I understand this correctly, you ran the car with the drain port of the accumulator disconnected. If that's the case, your problem is not the accumulator. If it was, fuel would drain out the bottom as there would be a leak in the diaphragm. Have you run a residual pressure test on the fuel line before it reaches the accumulator? I would suggest you do that before you spring for an expensive part you may not need. If you cannot maintain residual pressure in the line between the pump and the accumulator, your problem in the check valve--much cheaper to replace.

You say you don't have an in-line check valve but many fuel pumps have an internal check valve, as may yours. It is possible to add an in-line check valve.

[npresley]

I believe that is correct. How would I check the residual pressure in the line between the pump and the accumulator?

[T77911S]

that is done with the gauges connected to check pressures. WUR-FD

[npresley]

any different hook-up, or test than I have already done? or would I purchase an external check valve, install it, and re-test.

[timmy2]

Same test. Install check valve and test.