When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 1985 F150 with 300ci six in it i replaced the original distributor with a Duraspark distributor it came with the truck when i bought it it is new and has two diaphrams on it, the control unit that came with it was new and has DY184CS 35002512-753 Recitor USA printed on the side, with it all fitted and timed up the engine runs fine i have the vacume hose connected to the rear diaphragm and when i open the throttle and the vacume advance moves the base plate to advance timing the engine cuts out? i have removed the distributor and tested it in the bench for broken wires and or bad continuity as the base plate moves but no fault found, at present i run without the diaphragm conected and it is fine but anyone any idea why it cuts out as soon as the advance kicks in? is the control box the right one? any help would be much appreciated.
I know very little regarding the two diaphrams distributor control except this was used on older systems and one was used, I believe, to retard the timing at some point.
I have had experience with having misfire problems when the vacuum advance comes in... my 1986 4.9L was also retrofitted to DS2 and the timing was advanced too far when the engine speed would approach 1700 RPMs under light load, causing very bad misfiring. If the throttle was opened quickly [full throttle], the vacuum would drop, the timing would retard and the missing would cease until once again, the load was lessened. Mine, too, worked well without the vacuum line being connected [but plugged!], however, the fuel mileage will suffer.
You can try retarding the static timing a bit, but ultimately will benefit the most with a proper "recurving" of the distributor.
Also, using a vacuum gauge, check what reading you get with the hose attached to the carburetor port being used for the distributor. Some older carburetors used what I have been told is venturi vacuum, rather than the normal vacuum. The 1970 Carter YF, which I use, measures between ~5 and 11-12" of Hg rather than 0-25" which better represents what one would see in others. The 25" is when the engine is decelerating.
Hope this is helpful! By the way, my vacuum advance is connected to manifold vacuum due to what was described previously.
The short answer is to try putting the hose on the other connection, the one on the end of the vacuum canister.
While it is often called a dual diaphragm vacuum advance ... my gut tells me it might also be a single diaphragm with connections on each side of the single diaphragm to both "pull and push" the diaphragm.
They had some weird setups that they used with the dual diaphragm setup, but Jim is correct, move the hose to the other side and leave the rear one open.
Right a bit challenged with the computer still trying to get the hang of the site, i have a Holley 390 cfm four barrel but irrelavant as i have the vac pipe disconnected and plugged and if i remove the diaphagm and move the baseplate by hand it cuts dead as soon as i move the baseplate but cuts back in when returned to orriginal position? i have checked the distributor on the bench for any break in the wires as the baseplate moves and that the baseplate moves in a circular ark so the gap does not change on the pickup from the rotor on the shaft all good?
If you retard the timing too much the engine probably will stall. Leave the dist vacuum disconnected, and loosen the lockdown bolt for the dist a little bit so it will twist with a little force applied. Start the engine and find out which way when you turn it the engine slows. Now take it and twist it abruptly in that that direction. Does the engine cut out like it has been doing? Whether you move the baseplate or move the whole dist body, there is not much difference.
Right Dave F i see what you mean advance the timing with the distributor base or the base plate is advance which ever you look at it, i did that and all ok i have been running with the diaphagm off the distributor all together and had the lever for the base plate locked up so as not to alter the timing as i was driving, if i move the base plate as the motor idles (to advance the timing as the diaphagm does) it starts to run very irratic as if the timing is totally out and then cuts out, if i replace the diaphagm without the vacume hose the motor will not run the difference being i lock up the base plate in the fully retarded position and when the diaphagm is fitted the base plate is advanced by about 3/8 of an inch and allthough i retard the timing to compensate for this movement it will not run with the base plate in that position it totally messes up the timing?
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Slideshow: The VelociRaptor Expedition gains a lift, upgraded suspension, Brembo brakes, and trail-ready equipment while retaining the stock 440-horsepower EcoBoost V6.
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Slideshow: Called the Fortress, the 850-horsepower pickup combines Raptor underpinnings with military-inspired features, survival equipment, and a starting price of $285,000.
