The Cold Start Device (CSD) has been discussed in the forum a number of times and seems to be of continuing interest, probably for good reason. The intent of this device is to assist in starting the engine, particularly when it is cold. It does this by advancing the injection timing by about 8 degrees when the injection pump is at rest. Doesn't matter what the temperature is despite the name. As far as I know it does advance the timing for start up reliably.
There is a problem with it though which causes the normal (running, not start up) timing advance to fail or partially fail or intermittently fail. This is very serious as the engine power and fuel economy are adversely affected when the the timing does not advance. Also, exhaust smoke will be much higher and the engine temperature will likely run higher, although this may not be noticed as these engines run unusually cool.
Jerry Lemond first brought our attention to this device by telling us to remove the shims and/or the springs in the CSD and the engine would run much better. I wondered what this could do besides rendering the CSD inoperable. Later, jimmyguitar told us he had removed his CSD altogether and his truck ran very much better. OK, so now I am interested enough to take a hard look at the CSD and the injection pump.
What happens when the CSD causes trouble is that it allows fuel to leak past an internal seal to a fuel return port. This, in turn, prevents the normal timing piston from being driven to an advanced position by the housing pressure. It takes only a little leakage in the CSD to cause trouble because the housing pressure is fed to the power side of the timing piston through a small hole, less than a mm in diameter.
If I am confusing you with tech talk you may want to take a look at the VE pump as there is a nice manual for it on line HERE. So far the poster has not finished posting the images but hopefully soon will. Also, there is a photo essay of the pump HERE. Neither of these sites discuss the type of CSD used on the P'up as it seems to be peculiar to them.
OK, we have trouble. So what to do about it? Well jimmyguitar took his off and so did our site owner, JoeIsuzu. One also can just disable it by removing the springs, shims and piston (husq_tech74 did this). Or one could (with some effort) replace the CSD with a manual unit from a VW pump. The down side to removing the CSD is that starting in cold weather and/or high altitudes will be more difficult. JoeIsuzu and jimmy seem to be getting along OK.
I am removing the CSD from one of my trucks now and will take some photos and make notes on the process. Stay tuned.
EDIT: Aug 2, 2009
Here is a photo of a pump on my bench showing the CSD.
Here is the way I did this job.
--Remove the splash pan from the front of the engine compartment. Jack up the right front of the truck and remove the right front wheel. Best to place a jack stand under the frame for safety.
--Remove the rubber splash shield from the inner fender wall.
--Now you can see the CSD
--Remove the fuel return pipe totally from the pump by pulling the banjo bolt at the top of the CSD and also the larger banjo bolt at the top of the pump. You will need to pull the two rubber lines off also.
--I took the CSD apart in stages because it is easier to deal with the spring loads that way. First, pull the center plug with a 10mm hex driver. Now you can remove the smaller center spring and any shims.
-- Now, remove the four cover bolts and remove the cover and the larger spring and shim. There will be some spring load here but not too bad.
--Pull out the piston. Note here that fuel will be slowly draining out of the pump while you are removing parts. There will be about two T shirts worth so be ready.
--More coming - - - -
EDIT: Aug 3, 2009
OK, I'm back. And before I finish this thread I need to tell you that I finished this job yesterday and drove the truck to work today and found that it does NOT start as easily as before I removed the CSD. So, I conclude that the Isuzu guys knew what they were doing when they incorporated a CSD. Too bad they did not use a manual one. And, remember this is summer with temperatures here on our left coast around 75 degrees. Starting will likely be much harder come winter.
--The next thing to do is remove the CSD housing. This is tough as the nuts are hidden behind the housing and there is not enough space between the housing and the studs to use any normal wrench other than an open end wrench. And an open end wrench can not be gotten on the the nuts due to restricted swing space. Take a look at the next photo.
The above photo was taken of a spare pump on my work bench so you can not see the restricted wrench space. But, as Jack said to me 'the CSD gets in its own way'. (Jack, how did you get your CSD off?) So, what to do? What I usually do. I made a tool. I ground down a cheap 10mm box end wrench to a slimmer and trimmer size so that I could get it on the nuts. The box wrench has more angular accommodation than an open end wrench.
--This wrench can now be gotten on to the nuts. I loosened the rear nut from the engine compartment and the front nut from under the truck. Then I could run the nuts off with my fingers and, voila, the CSD is off.
--The O ring is in good shape as I overhauled this pump just a couple of years ago. So, now one needs to put a plate over this hole in the pump. I chose to make one of 1/4 inch aluminum. Perhaps 3/16 would be strong enough. I chose not to use a cover from the other side of the timing piston as these were designed for a much lower pressure. I do admit, though, that they appear to be strong enough. Here is the finished cover.
--And here is the cover in place.
--One thing left to do. The fuel return banjo fitting must be modified and reinstalled. I cut off the hard line that ran down to the CSD and made a cap and silver brazed it in place. This could also be soft soldered as the pressure in the fuel return line is low. Jack used RTV to plug his. Here is the modified banjo fitting.
This finishes my thread on removing the CSD. I would encourage anyone thinking of this to consider it carefully because:
--Removing the CSD will make your truck harder to start most times, especially when cold or at high altitudes.
--It is tough to get off.
--It would be even tougher to put back on, although I think it could be done.
--It may not be misbehaving. These seemed to have worked more or less OK for about 15 or 20 years but then gradually developed leaks in their seals which are hard to fix. I have tried to fix them and the results are very iffy. If you are making good power and your fuel economy is 30 mpg or better your CSD is probably OK. If you have poor power, fuel economy is down, you are smoking a lot and maybe performance is erratic, it may be due to the CSD. Check out all other possibilities first.
Paul
PS-- I will look forward to reports on starting and performance from all of you who have removed the CSD.
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EDIT: Aug 7,2009
When you remove the CSD and want to time the engine using a travel gage in the head plug the 15 degree (fed) or 13 degree (ca) timing specified by Isuzu will no longer be right. This is because the Isuzu spec allows for the approximate 7 degrees of advance provided by the CSD and that is no longer there. So what you need to do is time the engine for 0.5 mm lift at 8 degrees BTDC. And this will now be the same timing as you used to have with the CSD.
Timing at 15 degrees with the CSD removed is way too far advanced and will make a very rattle-ee engine.
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Edit: Dec 19, 2010 as a clarification to the above timing info:
If you have removed your CSD and not moved the pump on its mount your timing will still be correct. Removing the CSD only changes the 'engine at rest' timing. So, if you have removed your CSD and check the timing at rest you will find it to be at about 8 degrees BTDC. Likewise, if you wish to set your timing after removing the CSD, it should be set to 8 degrees BTDC.
Paul
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Edit: Nov 9, 2011 for more timing clarification when removing the CSD from a TURBO pump.
If you have disabled the Isuzu CSD on a turbo pump or replaced the Isuzu CSD with a plate or a VW CSD and wish to check or reset your injection timing the right setting will now be 3 degrees BTDC for 0.5mm of plunger lift. If you have the VW CSD, it should be in the retired position before doing a timing check.
This is different than the 8 degrees I recommended for a n/a engine because the Isuzu timing spec for a turbo engine is 10 degrees BTDC. The 10 degree spec is for a pump with the Isuzu CSD intact. Without the Isuzu CSD you must subtract about 7 degrees of CSD advance from 10 degrees to get the proper 3 degree timing for the turbo engine.
If you have only done the CSD disablement or removal you will not necessarily need to reset the timing as there will be no change in the timing when the engine is running. The above discussion is only for checking or resetting the timing if you have disabled the CSD.
Paul
