Re: HPDI surging
nope, I dont have it here. I have never seen one fail.<br /> I suspect its another salesman myth.<br /> but if you suspect it just remove it and either add a double ended hose barb or replace the section of fuel line from the engine filter to the pump intake.<br /> a quick run with a vacum guage attached at the pump intake will find air leaks or restrictions, the aniti siphon valve will drop 1"Hg or so and a good water seperator will drop 1/2"Hg or so and the total system vacum for that motor as measuered at the low pressure pump intake is 4"Hg, any more and its restricted. so we know that at or near WOT the system should have 1 and 1/2"Hg and less than 4"hg, less indicates an air leak and more indicates a restriction.<br />see how simple this is. one test confirmed or eliminated 2 possible causes.<br /> so lets look at the facts you have stated, and not knowing exactly where the fuel primer bulb is located its dicey.<br /> but so far the facts you stated, one engine surges and loses power,2 you can pump the primer and it runs normally.<br />from fact 1 and 2 I deduce the VST has no fuel to send to the HP pump thus a loss of fuel at the injectors which will set a code 25.<br /> so now I will look at the bulb itself, as you did NOT state the bulb was sucking flat I wont assume any restrictions down stream of the primer bulb.<br />means most likly the fuel system between the liquid level in the tank and the bulb is ok. now whats between the low pressure pump intake and the tank end of the primer bulb.<br /> thats where I would look.<br />its still possible that a partial restriction between the liquid level and the bulb exists but usually it makes pumping the bulb difficult and the bulb recovery very slow.<br /> sometimes its helpful,especially for the novice, to write down on paper what the symptom is, what helps or does not and what the system has to do then what its not doing.<br /> an example is on a C55 that was whopping me, someone else had replaced the flywheel,timer base assy and CDI with factory new stuff. the problem was with the trigger wire attached to the CDI as desined it created a no spark issue. I called my RTA looking for information on the trigger circuit function, next thing I know he was asking if I had sqirted premix down the carbs. I had to ask him why would I do that for a no spark condition?<br />the point is dont get so bogged down in details you forget what the low pressure side of the fuel system does.<br /> in other words the vapor seperator does not care how the fuel gets there as long as it does.<br />but as a maint item you may also wish to clean the VST filter and replace the medium pressure filter, DO NOT use a screw type clamp on the hose for the medium pressure filter.<br />as the hose expands and contracts with 50 PSI it tends to make the rack of the clamp eat into the hose and get loose. you really dont want it to pop off with 50PSI of pressure.
