QuestionHi Dick ! You helped me greatly with a turn signal question on my '36 Plymouth P2. Now I have a windshield wiper question. I have heard talk that I can improve wiper performance by installing a double action fuel pump and using it as the vacuum source for the wipers. Is this true ? Can I simply buy and install a DA fuel pump on my '36 and run the wiper vacuum line to it instead of the carb ?
Thanks again.
AnswerYes, this is true, but there are a couple of things you will want to know about it:
1. The improvement will be that the wipers won't be so likely to stall on a hard uphill pull, because the mechanical pump will produce vacuum regardless of how hard the engine is pulling. Without the mechanical pump, the vacuum drops off to nothing or close to nothing at full throttle operation (because the butterfly valve will be wide open, allowing atmospheric pressure into the intake manifold unrestricted). On flat level driving, there will be little or no improvement. If your wipers are not satisfactory in flat, level driving now, doing this won't solve the problem. If that is your case, you need to send the wiper motor out to one of the vendors who rebuild them - I use Kent Jaquith's "Cleansweep" of Zillah, Washington, but there are others who do this work. I am very satisfied with Kent's work on my old Packard wiper motors. I know David Ficken in New York also does good work. You may find the wipers are satisfactory after this is done, and save yourself the trouble of tracking down a dual action pump that fits your engine.
2. To install the mechanical pump, you would remove the single action pump and replace it with the double action pump, but you will then have to re-route the vacuum wiper system supply line to the correct fitting on the mechanical pump, and add an additional line from another fitting on the pump to the currently used fitting on the intake manifold or carburetor base - in other words, the addtional pump is in "series" with the intake manifold vacuum source, not instead of that source. To identify the right fitting, you will have to study the marking on the pump fittings. The line for the wiper system will probably be labeled "in" ( meaning air goes in here ) and "out" (meaning air comes out here) - this one goes to the current vacuum fitting at the base of your carburetor (direct intake manifold vacuum). If there is no marking that makes sense to you, it is OK to start the engine and use your finger to block each fitting - one will pull vacuum against your finger, the other will puff out air with each engine revolution.
3. A dual action pump may not have been offered for your car, but I suspect it was available for the more expensive cars that used basically the same engine block, such as the 6 cylinder Chryslers for the same or similar years. My parts book shows pump number 588 for all 6 cylinder Chrysler Corp cars back to 1940 - it may be correct for your car also, (my book doesn't go back that far) but I think that number is for a single action pump. I think you should check with Andy Birnbaum - he will know and may have the right pump for you with dual action.
I hope this is helpful,
Dick
