Author Topic: Warm Running Device (Read 16038 times)

DavidBrough · « **on:** January 13, 2012, 18:49:33 »

I’m slowly working through the full rebuild of my car and thankfully now have it running but have a problem with the WRD on the injection pump and would like to seek a bit of advice/reassurance.

The car starts and runs well cold but the WRD is not shutting off the airflow through the little filter even though the water flow is good and the tower gets very hot. This is where I will trot out the old favourite in that it was all OK when I took it apart, ha ha. That said I have had the IP rebuilt and recalibrated but I’m not sure how that can affect the operation of the WRD as it seems to be a closed operation device. The answer may be as simple as placing more shims on top of the piston which I did but all I had was a 0.8mm washer so I used that and whilst it was better it still didn’t completely shut off the air flow. I purchased a new thermostat but that is exactly the same as the old one so I’ll try a thicker washer but an extra 1.0/1.2mm is likely to be needed and that really does seem a lot so I would be interested to know if this is common or unusual or if there’s anything else I should check.

I’ve set the ignition timing to 0deg at tick over with a strobe, the CSV is not leaking all cylinders are firing with NGK BP5ES plugs and have 165 psi compression and it starts easily when cold.

wwheeler · « **Reply #1 on:** January 13, 2012, 21:01:58 »

As a point of reference, the WRD on my '68 requires the round shim to be a minimimum of .025" before it will shut off. This was determined by actual testing. Even then, it may leak just a bit. Right now I have .040" and I am probably going add another .005" or .010" to get it to shut off just a bit earlier. So for my engine, .040-.050" is normal. I recall it came back from the rebuilders a few years ago with .045" worth of shims.

I would expect some varience between engines depending on wear and operating conditions. A worn thermostat rod would require more shims. From memory, I believe the temperature that the WRD is supposed shut off at is around 160*F. But check the BBB to be sure. Mine shuts off now at about 170*F or so.

DavidBrough · « **Reply #2 on:** January 13, 2012, 21:23:06 »

Thanks Wallace that's useful, I didn't measure the shims already in so I don't know what the total is but as you added about the same as I may need to it doesn't seem so bad. The main thing I can't understand is how a closed system could change so much as it did close off before I took it apart and all it seems to do is react to hot water so I can't quite see what could have changed to require what seems to be double the amount of shims.

wwheeler · « **Reply #3 on:** January 13, 2012, 22:13:47 »

I have a few spare WRDs and because of that I have a few shims to select from. It seems like there was one thick one (.020", .51mm) that was always used. That must be a baseline and you go from there. Since the piston is aluminum and the thermostat rod is hardened steel (presumably), you would have to always have a shim installed. Otherwise, the thermostat rod would quickly bore a hole into the soft alumnium piston.

I don't know why it would have changed so much?

Benz Dr. · « **Reply #4 on:** January 14, 2012, 05:28:11 »

Maybe the thermostat is getting weak. That's the one thing that can change given that everything else remains the same.

DavidBrough · « **Reply #5 on:** January 14, 2012, 07:31:25 »

I did wonder about that so I've tried a new one and it made no difference so I assume that bits OK.

stickandrudderman · « **Reply #6 on:** January 14, 2012, 10:38:35 »

Plenty of WRDs don't shut the air off completely, it's not usually a major issue, you just make an adjustment with the idle air bleed screw as normal. Try coating the piston with copperslip and see if the air bleed stops. If it does then you know that you've got a worn cylinder/piston in the WRD but I wouldn't worry about it too much.

DavidBrough · « **Reply #7 on:** January 14, 2012, 10:54:35 »

Quite a large part of the problem for me is how can it change so much by just sitting in a box for a year, now I know the answer is clearly it has and to a very large extent such that the warm running is exceptionally rich pointing to much more travel being required to also fully move the rack to its warm run position as well as closing off the air flow. I think that trial and error will inevitably be the answer by trying to obtain some more shims or putting progressively bigger washers on the piston to see what happens.

Cees Klumper · « **Reply #8 on:** January 14, 2012, 19:41:36 »

Reading through this now, I think I may have located a persistent little problem that started a few years ago: when warming up, but not yet fully warm, the car sputters as if it's about to die when at a traffic light for instance. I've tried a bunch of things to correct it but nothing seems to help and it was never this way over 10 years of ownership. The WRD shuts off, but perhaps a bit too early, could that be my problem? I suppose trying a new thermostat is never a bad idea, it may do the trick. Interested in any views.

hands_aus · « **Reply #9 on:** January 15, 2012, 01:35:57 »

If I remember correctly, the inj pump replacement thermostats changed a bit requiring the alumium washer under the thermostat housing they sit on to be drilled / sized so that the thermostat can sit properly and be at the correct height.

This was discussed previously

Iconic · « **Reply #10 on:** January 15, 2012, 14:43:33 »

David,
I may be missing the point here, but have you:
1. Checked to make sure the piston that cuts off the airflow, moves freely throughout the entire range?
2. Check the "heat feeling" or thermostat device in hot/boiling water to insure you are getting the the rod to come out the correct amount? (From memory it is supposed to move 4 or 6 mm ??)

DavidBrough · « **Reply #11 on:** January 16, 2012, 12:24:41 »

Bob/Iconic

The piston moves freely and I tried a new thermostat which made no difference and the shim end seemed to fit into the shims OK. I've now found a 1mm washer (existing shims 1.3mm) and with that added the air finally shuts off at about 85 deg so perhaps I just need another 0.2mm or so, I just need to find a source of shims to try. It's odd though that the system used to work fine with just 1.3mm of shims and now seems to need almost twice that to do the same job.

wwheeler · « **Reply #12 on:** January 17, 2012, 16:42:51 »

Cees,

I have a similar problem. When my engine first starts when cold, it is rich as you would expect and idles at 900RPM. As it starts to warm, it leans out slightly and the RPM picks up to 1000. Then the engine warms up enough where the idle begins to drop back close to normal at 800 RPM. So far so good.

Then the engine will begin to run very lean so much so that the idle drops to 500-600 RPM and there is a noticeable miss. Doing the split linkage confirms this and if I add just a bit of fuel, it runs great. If I let that car idle in the garage, the lean takes a long time to go away. If I drive it, the lean problem goes away much faster. After that, it runs with a good mixture and RPM at idle. Whether I let it idle or drive it, it will always go throught the lean period. Idle is the only speed range that has this lean period.

So if I add more fuel via the IP idle knob, it is too rich at warm idle. I can add more oval shims to the WRD but then it is very rich when running cold. The other thing I am going to do is change the round air valve shims in order to minimize the time the lean period exists. I am thinking I will add more shims to shorten the time the WRD is active but I don't know at this point. It seems as though it is all a balancing act. Thinking like a mechanical injection pump is not easy!

Cees Klumper · « **Reply #13 on:** January 17, 2012, 20:00:25 »

Thanks Wallace, this indeed seems to be the same problem. I will tinker with the shims etc and see where I get.

awolff280sl · « **Reply #14 on:** January 17, 2012, 20:36:12 »

Wallace, you've described exactly what my 280sl does as well. The phenomenon where driving during the "lean period" cures it is especially mysterious.

wwheeler · « **Reply #15 on:** January 17, 2012, 21:13:21 »

Being a tinkering engineer, I have also altered the air valve opening in the WRD housing. I have opened up the slot to let more air in when the piston is at its most cold position. I did this by filing the slot verrrrrry carefully. My thought here is to allow more air in when cold so that I can add more oval shims. This should keep the mixture when cold about the same but be richer during that strange lean period. Who knows.

I am just about to reinstall my IP after retiming it and plating just about everything it seems. I should have it running by the end of the month, and I will know if it works at that point. This was a spare WRD housing by the way. I don't have enough confidence to do it on my original!

My car didn't always have the lean period, but only appeared after I have fine tuned the mixtures over the years. I am thinking that I have been too concerned with the engine running rich when cold and I may have over compensated. Oh well, I can always put the old WRD housing back on if it doesn't work.

Cees Klumper · « **Reply #16 on:** January 18, 2012, 05:22:25 »

Wallace - you said that during the period where the engine stumbles, adding a bit of fuel doing the split linkage test imrpoves things. In my case though, I have to add air. So apparently the imbalance can go both ways.

twistedtree · « **Reply #17 on:** January 18, 2012, 13:06:00 »

From all I've read on this site, and from a small amount of experience myself, I think the way the WRD works is:

1) Changing the round internal shims/washers adjusts the progress of the WRD relative to temp. At a minimum, you need to be sure there are enough shims/washers so the air passage closes completely when hot. But regardless of how you set these shims, the air and fuel still change in tandem, and their relative proportions (i.e. mixture) does not change. This is because there is a fixed distance between the air plunger which controls air flow, and the protruding pin which controls fuel enrichment.

2) Changing the oval shims between the pump body and WRD adjusts the warm-up mixture by moving the pin in or out relative to the FIP without changing the air plunger position. This changes the mixture.

To get things set up, I think the steps are:

1) Be sure the WRD device is not seized up, that the plunger moves as the thermostat is heated, and that the air passage closes completely. Take the thing off the car, attach a little hose to the air fitting, and dip the thermostat in a pot of water with a thermometer. Heat the water, and try blowing through the hose as it warms. You'll feel the passage become restricted and eventually shut off at about 160F. If it doesn't shut off then, you'll been to adjust shims.

2) Put everything back together, warm up the car, and be sure you are well tuned for warm running - mixture, timing, dwell, no vacuum leaks, etc. As the car is warming up, periodically check the WRD air intake. It should be sucking air for a while then stop once the car passes 160F (roughly).

3) Now you need to let the car get cold - completely cold. Start cold, and check mixture as the car warms up. Check at several temperatures, and each time write down whether it's lean or rich (use the split linkage test). Once warm, the car should return to proper mixture as in step #2. If it doesn't, then you need to figure out why.

4) Based on the warmup mixture results and notes taken in step #3, adjust shims between the WRD and FIP body to richen or lean. Then you need to let the car get cold again and recheck.

Cees Klumper · « **Reply #18 on:** January 18, 2012, 20:06:24 »

Twistedtree's post for me has the makings of a technical manual or 'tour' article, that is great.

One thing we have not discussed yet is the air filter on the WRD - could that filter slowly getting restricted be an explanation for the symptoms some of us are experiencing (with uneven warming up behaviour in terms of air/fuel mixture?)

stickandrudderman · « **Reply #19 on:** January 18, 2012, 20:36:04 »

It has been discussed quite recently:
http://www.sl113.org/forums/index.php?topic=15630.0

twistedtree · « **Reply #20 on:** January 18, 2012, 21:08:48 »

Actually, I'd be willing to do that. There have been some really good new insights into the WRD operation recently, particularly by JA17 and JHuber. I relied heavily on their contributions working on my cars and would be happy to return the favor by compiling and editing the material.

Cees Klumper · « **Reply #21 on:** January 19, 2012, 08:47:56 »

Quote from: stickandrudderman on January 18, 2012, 20:36:04

It has been discussed quite recently:
http://www.sl113.org/forums/index.php?topic=15630.0

Thanks Stick - sorry I missed that.

Twistedtree - I think it would be great if you would take the time and compile everything into a tech article.

Meanwhile, I will replace that small filter and see what happens.

wwheeler · « **Reply #22 on:** January 19, 2012, 20:45:14 »

Thanks twistedtree for adding that as it will be a great addition. There is some there now but it needs the additional info. You also might add the work done by Jeffc280sl in regards to the spring loaded plunger. I can't seem to find it now but it talked about how there is a stop in the pump for the spring loaded plunger. Once the plunger reaches the stop, it can no longer lean the pump further. The spring loaded feature on the plunger absorbs the force from the thermostat rod as it keeps pushing down by rising temperatures. Eventually, I guess the plunger spring force and the thermostat force balance out and the whole assembly becomes static.

twistedtree · « **Reply #23 on:** January 19, 2012, 20:50:47 »

Yes, that's the new insight I was referring to. Sounds like I credited it incorrectly. I agree the info is all out there - it's just a matter of gathering and organizing as reference material in the Tech Manual.

wwheeler · « **Reply #24 on:** January 20, 2012, 05:22:12 »

Twistedtree,

I found the post I was talking about earlier. Only to discover that you were also a part of it later on. Good pictures of the stops and spring loaded plunger. That was a really good thread and pretty much explained the WRD function. Thanks again for putting that info in the manual!

http://www.sl113.org/forums/index.php?topic=9244.0

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Author Topic: Warm Running Device (Read 16038 times)

DavidBrough

DavidBrough

DavidBrough

DavidBrough

DavidBrough