Possible WUR issues.

[RamblinDMC]

Calling all K-jet experts! I think my WUR is not working correctly. After the car has warmed up it acts like it starving for fuel under heavy acceleration. I hooked up a k jet pressure test kit and the pressure goes from about .5 bar to about 3 bar once it has warmed up. Should the vacuum enrichment be working after warming up?

Thanks
Jayce

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[Bitsyncmaster]

Sounds like your pressure is close to correct. I get about 50 PSI control pressure warmed up (3 bar = 44 PSI).

Ignition vacuum advance should only occur after engine warmup and not at idle (idle switch not on).

I assume you have set your mixture via dwell reading the lambda system.

[RamblinDMC]

I have adjusted my mixture, however my the reading on the dwell meter doesn't change when I turn the adjustment screw.
I am also running open loop.

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[Bitsyncmaster]

I have adjusted my mixture, however my the reading on the dwell meter doesn't change when I turn the adjustment screw.
I am also running open loop.

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Dwell will not change adjusting the mixture if your open loop. Your probably running to lean if your problem is poor acceleration. I'm guessing you adjusted mixture for best idle. You will need to adjust it richer.

Make sure your ignition timing is correct with the correct advance (vacuum and mechanical).

[RamblinDMC]

Adjusting the mixture screw to make it run richer doesn't always help.
Interestingly, after the car warms up, and I connect the vacuum line going to the spark advance to the WUR so now that I have vacuum enrichment, the car runs wonderfully.

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[Bitsyncmaster]

Adjusting the mixture screw to make it run richer doesn't always help.
Interestingly, after the car warms up, and I connect the vacuum line going to the spark advance to the WUR so now that I have vacuum enrichment, the car runs wonderfully.

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I was adding that to my post. Correct advance will give you a lot of power if it was not working.

[RamblinDMC]

For some reason it runs better with the vacuum advance disconnected and vacuum enrichment on the WUR active while warm.
I do think if the timing was off, it would always run bad. The car starts and runs just fine while cold.

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[Soundkillr]

If the car has vacuum going to the wur (when hot) then the switch under the manifold has failed. The car should not have vacuum on the wur when hot, only when cold. Running like this will result in the car loading up and act like hesitation. Symptoms are runs fine cold, and stumbles hot....

[RamblinDMC]

It doesn't have vacuum while hot. However if i give it vacuum it runs better for some reason.

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[Horsebox]

I have adjusted my mixture, however my the reading on the dwell meter doesn't change when I turn the adjustment screw.
I am also running open loop.

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What did you do to your mixture screw? Ended up turning clockwise or anti-clockwise?

[RamblinDMC]

From my understanding. The dwell reading shouldn't change if the o2 is disconnected.

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[Horsebox]

I agree, but what did you do to your mixture screw?

[RamblinDMC]

I adjusted it for the smoothest idle.

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[Horsebox]

A noble cause, but what did you do to your mixture setting? It's a simple question and we just want to help.

[RamblinDMC]

What did I do to my mixture setting? Well i do notice that it runs better set richer, but it makes it idle hunt.

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[Soundkillr]

Based on what I'm hearing, it sounds lean. Does the fuel enrichment switch work?

[Jonathan]

If you are trying to get the engine to run as it was designed to, doesn't it make sense to get the things you know are disconnected or not working resolved first, and THEN move onto other areas you suspect are a problem?

I personally think the engine design along with the fuel system was fine for what it is and that it'll run fine too if it is all in order. If a piece or two is out of order on the other hand, then trying to get it to run smooth, or nice, or whatever in spite of that is only going to have you (and us) chasing your tail.

Not saying this is a waste of people's time trying to help, but if you know a portion of the engine is disconnected or not functioning, then fix that first. Si?

[RamblinDMC]

Yes' the fuel enrichment switch works, however it is only pressed under full throttle.
Most of the car's hesitation issues are at 1000 to 2000 rpm.

The fact of the matter is, the engine is starving for fuel under moderate to heavy acceleration. Even after everything else in the fuel system had been replaced and is in working order as far as I know.

I have modified the vacuum hose routing to allow for CPR fuel enrichment even after the engine has warmed up. I've used a needle valve inline with the vacuum hose to keep the fuel from becoming too rich.

Now the car runs and drives better than it ever has.

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[NckT]

I have adjusted my mixture, however my the reading on the dwell meter doesn't change when I turn the adjustment screw.
I am also running open loop.

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What was the dwell reading? What was the setting on the meter?

If you had the meter set to "4 cylinder dwell" and you read approx '45' on the meter, then it's likely your oxygen sensor is disconnected and you are running open loop, and connecting the vacuum line to the cpr may reduce the control pressure to riven the mixture to compensate for your lean mixture adjustment.

If you had the meter set to "4 cylinder dwell" and you read approx '52' on the meter, then it's likely you have a stuck/ short full load throttle switch/ lambda switch or a short to earth on the wiring. This would fix the dwell setting and the oxygen sensor feedback will not be used by the fuel computer.

State if you have a catalytic converter in the exhaust and if you've checked for correct operation of the thermo-vac switch.

Good luck

Nick

[Soundkillr]

Yes' the fuel enrichment switch works, however it is only pressed under full throttle.
Most of the car's hesitation issues are at 1000 to 2000 rpm.

The fact of the matter is, the engine is starving for fuel under moderate to heavy acceleration. Even after everything else in the fuel system had been replaced and is in working order as far as I know.

I have modified the vacuum hose routing to allow for CPR fuel enrichment even after the engine has warmed up. I've used a needle valve inline with the vacuum hose to keep the fuel from becoming too rich.

Now the car runs and drives better than it ever has.

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Is the car boosted? My understanding of this technique is, it won't work unless there is boost pressure, or pressure pushing down on the diaphragm to mechanically trick the car to running richer....
not trying to derail your thread, just want to make sure it is working for you, without giving a spike, then leaning back out.
without pressure the car will richer for a bit, but then leans back out...

[RamblinDMC]

What was the dwell reading? What was the setting on the meter?

If you had the meter set to "4 cylinder dwell" and you read approx '45' on the meter, then it's likely your oxygen sensor is disconnected and you are running open loop, and connecting the vacuum line to the cpr may reduce the control pressure to riven the mixture to compensate for your lean mixture adjustment.

If you had the meter set to "4 cylinder dwell" and you read approx '52' on the meter, then it's likely you have a stuck/ short full load throttle switch/ lambda switch or a short to earth on the wiring. This would fix the dwell setting and the oxygen sensor feedback will not be used by the fuel computer.

State if you have a catalytic converter in the exhaust and if you've checked for correct operation of the thermo-vac switch.

Good luck

Nick

It was sitting around 45 on my dwell meter. I do have my O2 disconnected. My car still has the original cat, I would like to have it removed or hollowed out. The thermo vac switch is working as intended.

[RamblinDMC]

Is the car boosted? My understanding of this technique is, it won't work unless there is boost pressure, or pressure pushing down on the diaphragm to mechanically trick the car to running richer....
not trying to derail your thread, just want to make sure it is working for you, without giving a spike, then leaning back out.
without pressure the car will richer for a bit, but then leans back out...

My car is not boosted, not yet at least. I have a BAE kit to install sometime soon. From my understanding doesn't the vacuum pull the diaphragm down to allow for more fuel to travel to the upper chamber of the distributor. From my understanding, it looks like the fuel system is kept at a constant pressure regardless of fuel demand. It would just make sense to up the fuel pressure as the engine starts demanding more fuel. My car now runs better than it ever has. It would constantly stutter from 1000 to 2000 rpm under medium to heavy load. Most of my issue was, if I adjusted the CO screw so that it would run better, it would idle hunt and nearly stall. However, if I adjusted the CO screw for a good idle, it would run like crap. I needed to have a relatively leaner idle and somewhat richer under power. This continuous vacuum enrichment mod seems to have done the trick.

It did occur to me, why I am not able to set the idle richer, maybe because the idle speed control motor may be stuck, therefore leaving me with a too rich idle. I'll look into that before I decide to leave the WUR vacuum routing modified long term.

Thanks,
Jayce

[NckT]

I'd recommend you get a fuel pressure gauge and measure the main fuel pressure, followed by the control pressure test from the control pressure regulator (warm up regulator)

If it assists, I noted another similar fault that I traced to a faulty vacuum delay valve.

Good luck

Nick

[RamblinDMC]

I have a pressure test gauge and have verified correct pressures from both.

After the car has warmed up, the vacuum delay valve is no longer used correct?

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[NckT]

Including the correct control pressure to the temperature chart, as well as the vacuum deflection by applying a vacuum to the lower diaphragm chamber?

You're correct that the oem setup of the thermo-vac switch does not apply vacuum to the control pressure regulator when the engine is warm.

I'd recommend you get an exhaust gas analysis "pre-cat" and adjust to 1.0 to 1.5 % CO.
Or
Fit a new oxygen sensor and set the dwell of the frequency valve to 35-45 "4 cylinder dwell" on the multi meter.
I'll assume that the frequency valve is actually buzzing and you're not just reading the electronic switching to the frequency valve where it could be stuck.

Good luck

[Soundkillr]

My car is not boosted, not yet at least. I have a BAE kit to install sometime soon. From my understanding doesn't the vacuum pull the diaphragm down to allow for more fuel to travel to the upper chamber of the distributor. From my understanding, it looks like the fuel system is kept at a constant pressure regardless of fuel demand. It would just make sense to up the fuel pressure as the engine starts demanding more fuel. My car now runs better than it ever has. It would constantly stutter from 1000 to 2000 rpm under medium to heavy load. Most of my issue was, if I adjusted the CO screw so that it would run better, it would idle hunt and nearly stall. However, if I adjusted the CO screw for a good idle, it would run like crap. I needed to have a relatively leaner idle and somewhat richer under power. This continuous vacuum enrichment mod seems to have done the trick.

It did occur to me, why I am not able to set the idle richer, maybe because the idle speed control motor may be stuck, therefore leaving me with a too rich idle. I'll look into that before I decide to leave the WUR vacuum routing modified long term.

Thanks,
Jayce

It does pull some fuel, but as I was told, it will equalize and balance out. There is more you have to do, to get enrichment constant when under throttle. I can send you the article. From memory you will need your one way check valve, boost going to the regulator, a solenoid and a relay. I did the enrichment method on my car (it was boosted) and it did work, but without the solenoid the argument was it would eventually level out causing a short fuel spike and then do nothing. Who knows. I did follow it as instructed and got a good bit more fuel as measured by my afr.

[Bitsyncmaster]

It sounds like you need to get the WUR vacuum working correctly and then adjust your mixture. If you change anything that affects mixture, you need to go back and adjust mixture to your liking.

More control pressure results in leaner mixture. The WUR is preset to deliver a preset amount of rich mixture which was designed assuming the normal mixture setting was correct holding 14.7 AFR. If your running richer (since your open loop) then you may find the cold engine warm up is to rich unless you can adjust the WUR. There is an adjustable electronic WUR but it cost $500.

Another option if you want to stay with a richer mixture is to install a wideband unit which feeds the stock lambda ECU. That gives you the option to accurately set and hold your wanted mixture.

[RamblinDMC]

Including the correct control pressure to the temperature chart, as well as the vacuum deflection by applying a vacuum to the lower diaphragm chamber?

You're correct that the oem setup of the thermo-vac switch does not apply vacuum to the control pressure regulator when the engine is warm.

I'd recommend you get an exhaust gas analysis "pre-cat" and adjust to 1.0 to 1.5 % CO.
Or
Fit a new oxygen sensor and set the dwell of the frequency valve to 35-45 "4 cylinder dwell" on the multi meter.
I'll assume that the frequency valve is actually buzzing and you're not just reading the electronic switching to the frequency valve where it could be stuck.

Good luck

Yes everything checked out okay.

I probably could use a new O2 as the car still has the original one installed. My car seems to run worse with it connected.
Thanks for your help!



It does pull some fuel, but as I was told, it will equalize and balance out. There is more you have to do, to get enrichment constant when under throttle. I can send you the article. From memory you will need your one way check valve, boost going to the regulator, a solenoid and a relay. I did the enrichment method on my car (it was boosted) and it did work, but without the solenoid the argument was it would eventually level out causing a short fuel spike and then do nothing. Who knows. I did follow it as instructed and got a good bit more fuel as measured by my afr.

Thanks! Hopefully I can get together enough money to purchase the turbo rebuild kit this year.



IIt sounds like you need to get the WUR vacuum working correctly and then adjust your mixture. If you change anything that affects mixture, you need to go back and adjust mixture to your liking.

More control pressure results in leaner mixture. The WUR is preset to deliver a preset amount of rich mixture which was designed assuming the normal mixture setting was correct holding 14.7 AFR. If your running richer (since your open loop) then you may find the cold engine warm up is to rich unless you can adjust the WUR. There is an adjustable electronic WUR but it cost $500.

Another option if you want to stay with a richer mixture is to install a wideband unit which feeds the stock lambda ECU. That gives you the option to accurately set and hold your wanted mixture.


The vacuum routing was to the correct specs earlier, even then the car did not run correctly, even after adjusting the mixture. Previously, the car ran flawless cold, but after it got warm/hot, it began starving for fuel. It seems like the mod I made got rid of my fuel starvation issue. I'll look into installing a wideband sensor, and then reverting my vacuum lines back to the way they're supposed to be. Maybe then I'll have some more adjustability.

Thanks for all of your help!

[NckT]

Just to note that you can't install a wide band oxygen sensor direct to the oem fuel computer. The signal output is different.

[Bitsyncmaster]

Just to note that you can't install a wide band oxygen sensor direct to the oem fuel computer. The signal output is different.

Correct. You program the wideband electronics to simulate the narrow band output and drive the stock lambda ECU with that simulated output.