924Board.org

[jdub]

I'm back to the WUR -
Car running rough until engine temp gets to normal hot temp ( a few minutes)

There is no running difference in car when it's plugged in or not plugged in- at hot temps at least)

(before when i was inside the WUR, the fine screens were a little clogged and everything seemed to run better after I cleaned those) ,

Is the 12.4v running to it on the connector always supposed to stay steady, or is that where the internal heater is turned on and off ?
should it never change?



? thanks
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81 924 non-turbo

[larchie]

Measuring control pressure is the best way to check the operation of the warm-up regulator. With the wiring connected to heat up the regulator and the fuel pump running, the pressure should rise over the course of a minute or two to approximately 3.6 bar.

If the pressure does not rise in this manner, then look for a restriction in the fuel return line. Since your voltage to the warm-up regulator is good and if the return line turns out not to be restricted, then the warm-up regulator is faulty.

[larchie]

[jdub]

excellent- let me start with the pressure test again as you describe, the return line was fine last time you mentioned it
i'll get back
thanks
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81 924 non-turbo

[jdub]

sorry, a few weeks ago i wasnt very clear on results, so i just retested (car takes a while to run smooth while warming up for a couple min)

remember , for an 81, one area has slightly different #s needed

Test 1 for system pressure: (a) The engine was cold. The electrical connectors from the warm-up regulator and the auxiliary-air device were disconnected. The fuel pump was run and air was bled out of the system at the gauge by opening and closing the valve several times. (b) The gauge valve was closed, and the fuel pump run and you read 5 bar.
{Comment: this is OK.}
RESuLT TODAY: 5bar. good

Test 2 for cold -control pressure: (a) The engine was cold and the warm-up regulator wasn't hot to touch. The electrical connection to the warm-up regulator remained disconnected. (b) The fuel pump was run and the gauge value was opened so fuel should have been sent to the warm-up regulator.
{Comment: Your cold- control pressure should be about 1.5 bar. By now running the fuel through the warm-up regulator the gauge should hav
RESULT TODAY: 2.8 or 3 bar

Test 3 for warm control-pressure: (a) The plug to the warm-up regulator was reconnected (so that the regulator will heat up). (b) The fuel pump was run a
RESult Today: rose to 3.8 bar in less than one min. - but there was already about 1.5 bar lingering from previous test cold.

does this say anything bout WUR?

fuel return line volume was good recently tested.

thanks!!!
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81 924 non-turbo

[larchie]

I looked up the pressure values in James Weber's Solving Bosch Continutiou Injection System Problems and this is how they compare to the values you obtained:

Test 1 for system pressure: you measured 5 bar; Weber says 75 to 80 psi which converts to 5.1 to 5.4 bar, which seems good.

Test 2 for cold -control pressure: you measured 2.8 or 3.0 bar; Weber uses the temperature of WUR vs. PSI chart which I think is the same which is also in the Hanes Manual. If the warm-up regulator was 90 F degrees, the pressure should be 26 to 31 psi or 1.6 to 2.1 bar; if the warm-up regulator was 100 F degrees, the pressure should be 30 to 35 bar or 2.0 to 2.4 bar. But his figures are based on jumping the fuel pump without running the engine.

So if Test 2 was done with the engine running, the warm-up regulatore should have higher pressures since the diaphragm would be closing from the heat transferred from the WUR housing. Your reading of 2.8 to 3 bar would correspond to around 105 F degrees, which seems good since I think the temperature almost got to 90 F degrees yesterday.

Test 3 for warm control-pressure: you measured 3.8 bar; Weber tests with the pump jumped and the ignition on and rises accordingly, so that seems good also.

That's fantastic news since the warm-up regulator is probably around $330 to replace with core exchange. But unfortunately it doesn't solve your problem.
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As I recall you got good results earlier from the "leak-down" tests even with a faulty accumulator, and your resistance test of the heater coil was O.K.

I wonder however if the leak-down test was done with the valve open. If the valve were open then the warm-up regulator doesn't leak. If you were to test with the valve closed, i.e., testing the rest pressure, and there is leakage so pressure is not maintained, then many components would have to be checked -- but you have already checked most of them so far as I can remember, i.e., primary-pressure regulator, cold start valve, fuel injectors, and fuel accumulator. If if there's leakage on the leak-down test with the valve in the tester closed and pump off, the check valve is about the only thing left to be faulty. But this is all speculation without knowing the results of the leak-down test with the valve closed. Without trying to locate your earlier results, I think I do recall you did the test with the valve closed.

So the only other thing I can think of to test for the warm-up regulator is to test the regulator diaphragm by seeing if the regulator can hold a vacuum. Pull a vacuum with something like a Mityvac Hand Vacuum Pump from the vacuum connection (not the vent). Some of the list members might have other suggestions here, but if you don't have a vacuum pump, then you might be able to get a loaner from an auto supply. Disconnect the electrical plug, run the fuel pump. The warm-up regulator should hold about 0.6 bar of vacuum. If you don't get a vacuum, then its diaphragm is defective.

But I think your tests indicate well enough that the warm-up regulator is good.
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I still wonder, however ...

1. Does the engine run rough only on cold start?
2. Did the replacement of the accumulator cure the hot start problem?

[jdub]

sorry i couldnt get mu log in to work today on my work network today

so before doing the pressure tests yest., i had a day where i wasnt having the warm up problem . but i only drove once. ithought it may have been a fluke.

before that i had checked the WUR screens, and removed the finest one. they did look fine this time. i also had richened the A/F a little, since i had leaned for emmisions a few weeks ago.

well driving now, after the pressure testing last night, i've had NO problems with running rough.

weird.

to answer Qs: the replacing of Accum did not help the problem of hard starting after sitting an hour. (so it wasnt really an"hot start" problem really)
however, the Thermo Time Switch jumper switch work-around , and enrichung the AF seemed to have solved that prob.
plus, the sticking air intake meter plate getting freed up couldve been that problem, because eventually it wouldnt start at all, . i found i when seeing no fuel pressure from distributor. that is now fine.

My previous Leak Down was unreliable- it was giving mixed results, but unreliable because my Tester gauge is homemade and there' s an occassional slow seepage. it seems accurate for the shorter tests, like i gave last night

weird that now it's all fine, ( still need to use the TTS jump switch for it to start

I replaced the TTS with a Bosch off a Ferrari, with only an 8 second time, but that doesnt work, so i use the switch.
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81 924 non-turbo