1973 - 1979 F-100 & Larger F-Series TrucksDiscuss the Dentsides Ford Truck
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For some reason my posts aren't showing up. This will be my 3rd time to type this so it will be shorter.
fmc400, no I didn't check the timing. I wasn't aware that I needed to. The truck ran better than ever after I replaced the points. Will the truck still run if I remove the EGR plate and valve? It may help diagnose the issue. I wouldn't run it that way permanently, just as a diagnostic tool. I'll pull the EGR plate and valve and check it this evening for crud, wear, whatever.
My vacuum setup is a little different than what you posted. See below. It does show two ports on the modulator on the trans.
73 F100 Custom Explorer, 302, C4, 2WD
Last edited by Brewski; 08-07-2008 at 11:53 AM.
Reason: posts aren't posting
Anytime you adjust points, you have to check the timing. Because it is possible that the new points rest at a different position on the breakerplate after being installed, timing can be off by as much as a few degrees after replacing the points. The two procedures must go hand-in-hand.
It would be a good process-of-elimination to just cap off the EGR vacuum source for now to see if that affects the idle. That will let you know if yours is sticking open or somehow accidently connected to manifold vacuum, etc. If you have yours connected to the spark port properly, then it probably won't help your idle issues any because there is no vacuum at the spark port at idle to begin with. But sometimes simple checks like this can point out something you wouldn't have noticed before.
I took a look at your vacuum diagram, that is definitely one of the early types. Some ancient EGR systems incorporate an ambient temperature switch and electric vacuum switch like yours; some even go so far as to incorporate a vehicle speed sensor to control EGR, although it is very rare. The setup you have in that diagram isn't too much more complicated than my basic drawing. Basically the EGR is the same in the two diagrams. You have some extra hardware to control the vacuum to the distributor vacuum advance. There is a delay valve and an ambient temperature switch. However, if you have all that hardware plugged into the spark port like you should, it won't have any effect on your idle issues because the spark port has no vacuum at idle.
How is it running other than idle? Does it accelerate and drive okay?
I haven't attempted to drive it since it will not stay running and i have to pump the accelerator to keep it running. I don't want to shift it into gear at 2K rpms. Besides, it would likely die as soon as the rpms dropped after the shift anyway.
I actually have the temp. controlled vacuum valve. I found it laying on top of the intake manifold. No, it wasn't hooked up to anything. I didn't know what it was at the time other than something to do with vacuum but since the truck was running fine I considered it uneccessary. But decided to keep it "just in case". Like you said and I said before, the basics are there. I'm interested to see what I find tonight once I remove the EGR plate. From the way it sounds, it has internal passages too. Since I haven't seen anywhere that exhaust gas can enter the system, I can only assume that it occurs inside the intake manifold and through the spacer plate and somehow controlled by the EGR valve???? If that assumption is correct then there should be several internal passages within the spacer plate, correct?
You are correct. I don't recommend moving the whole plate, just disabling the valve. Hot exhaust gases enter into that plate from the manifold. If you remove the plate and drop the carburetor back down, you'll boil the fuel bowl. You will also have problems with the throttle linkage lining up. Now, there is a possibility that the plate has burned out from the inside and has an internal vacuum leak. You could just remove the carburetor and look at the throttle bores in the plate and see how flat it is with a feeler gauge and steel bar. My point is, don't put the carburetor directly on an EGR manifold with only a gasket in between.
A note on the spacer plates. There is a gasket between the manifold and the spacer plate, and then a gasket between the spacer plate and the carburetor. Many kinds are sold, but only one type is correct for each location. Between the manifold and the spacer plate should be a thick steel-woven gasket. It is the only gasket that can provide a proper seal and survive the heat of the EGR passages in the spacer plate. Between the spacer plate and the carburetor should be a 1/4" thick gasket with nylon bushings for the carburetor studs. This acts as a heat sink and is the only gasket right for this job. Carburetor rebuild kits come with spacer-to-manifold and spacer-to-carburetor gaskets, but they are paper and thin, and do not do their job at all. Sometimes they don't even line up. If you have these type gaskets under the carburetor, they're probably toast.
Did these idle problems just show up all of a sudden? Or was it after you put the cab and front clip back on? Anytime problems arise after major body work, a grounding issue is always something to look at too.
By the way I saw the rest of your gallery and you did an awesome job with that dash!
Thanks for the compliment. It was lots of work! I've checked all the grounding spots that are applicable and they all seem to be properly grounded.
The problem was very sudden. After reassembly, I was working on filling the radiator and trans with fluid. All the while the truck was idling just fine. Just as before the teardown. After about 30 minutes of idling I shut it down for about 2 minutes. It hasn't been right since.
That is GREAT info on the gaskets. I wasn't aware of the reasons for the differences in them. I'm glad you posted that. I doubt the ones from the kit are toast. The engine hasn't gotten warm enough that it was too hot to touch.
I'll pick up the correct gaskets if I can find them.
Hmm.... I may have uncovered a sneaky little problem! Take a look at the photos and let me know if you think the blocked passages may have something to do with my issue!?
The passage to the left of the screwdriver on the front of the intake may look open but it's full of black stuff. Also, the chamber in the EGR plate closest to the camera was packed full of dirt!! I chipped it away with a screwdriver. It was nearly rock hard!
I think you've found your problem. Look at the bottom-most throttle bore in your first picture. It's completely burnt through on the passenger side throttle bore. That spot isn't an exhaust passage; the EGR valve feeds exhaust to both bores equally in the center of the plate. It's burnt through where the valve mounts as well (pretty big hole!). You have a large, direct vacuum leak and after seeing that picture, I'm surprised your motor runs at all. Vacuum is leaking through that burnt opening in the passenger side throttle bore, through the exhaust collection cavity, out through the giant burnt hole in the plate. That plate is toast. Hopefully this will solve your problem, but if it doesn't, it's definitely something that needs to be taken care of regardless. You definitely need to replace it!
IDK, a problem so sudden doesnt seem like whats in the pictures. This is a shot in the dark, but my truck did the exact same thing. A little explaining first. if a motor is not getting enough fuel from say a plugged filter, pumping the gas pedal will kill the engine or damn near. Yet on the other hand... if you idle circuit is plugged and you pump the pedal all of a sudden it runs yea? This is because the carb is getting enough fuel, not the engine tho. If the idler cuircuts are plugged the only way the engine gets fuel is when you pump the gas thanks to the accelerator pump, which has to work correctly for obvious reasons. If you used compressed air when you cleaned your carb you probably got a piece of dirt or carbon lodged in the circuit... that or like mine, it was just crap in the bowl pluggin the jets off. My opinions are A) take the carb in, and have a shop soak it in real carb cleaner, (the kind that will disolve aluminum in about 10 hrs), as this will eat whatever is in the circuit, or B) as mentioned above, get an intake and carb for the beast. Also, a perk with the carb/intake route, no more EGR valve, and you get rid of a few vaccum lines while youre at it.
Note: if i said something already covered, i read the first two pages, skipped to the last and seen he still had a problem...
Regardless at this point. For all we know the leak might have been "sealed" off until it was disturbed in just the right fashion. Just enough of a 'knock' for the metal to finally give up.
Looks like a new valve, plate, gasket set is in order. If nothing else? It'll be fixed the right way, and removes yet another possible problem causer.
ND will be probably the best bet for research on the spacer itself. Napa sold me our EGR gasket, and Advance Auto was able to special order in the spacer to intake gasket. The spacer to carb gasket is a normally stocked item in most stores.
Don't bother going to Napa for the spacer. While they did at one time show a listing? It's long sense gone the way of the dodo. I got lucky with ours and located the exact one (cast iron) on eBay. (from a fellow ford parts collector trying to limit their stock of extras).
If I remember right? Sandersons Ford in AZ might have a few hanging around their back stock. Number Dummy hopefully can research this more. For what it's worth? Our local ford shops attempted to order in one, as the number was still in the system (the upgraded numbers) Sadly the order bounced back as being no longer available or made by Ford/Motorcraft. (heck, even had the right set of part ID's thanks to ND! However we tried several dealerships in my area, that the computer stated it was in stock--Only to drive all over central NYS to find "Sorry, we no longer have that part in the back room where we have the older stuff". One local shop gets high marks however. They called around and did a stock check to save me some running around. The older parts people knew EXACTLY what I was after, and why.
It'll take a bit of work, but I know there are more of those spacers in circulation.
The old girl is as follows:
1975 Ford F250 Camper Special
Rear Wheel Drive.
Last of the vin: W69956
I really appreciate all the help you guys have offered, this has been a major pain! I have another question though. Since the EGR plate was full of crud, isn't the intake also full of crud? It looks to me like I may need an intake as well to properly fix the problem.
The jets seem to flow air pretty well and I was able to get some carb cleaner in them so I THINK they are ok but I could certainly be wrong.
ND, the EGR valve # is still very clearly visible and is D3BE-9D475-A2B with a BIG 028 at the very end. Thanks for posting the info on those who may have some. I spent some time last night searching the web and the only thing I came up with was an Edelbrock intake that comes with the plate.
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