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Offline 74WagonMeadowGreen

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1978 Pinto backfire problem
« on: October 11, 2011, 11:15:48 AM »
I recently bought a 1978 Pinto 2.3L with 4-speed, no air, bare bones but not Pony. 52,00 ORIG. miles... absolutely stunning condition. Car ran OK, but no idle and backfiring on deceleration. I got home OK, and proceeded to check/replace certain things. It now has a new air pump (old one was very noisy), rebuilt carb, cleaned distributor, new wires, plugs, PCV, all vacuum hoses carefully, one-by-one replaced, fuel filter, etc. The timing belt was replaced at a Ford dealer by the previous owner. I CHECKED carefully both ignition timing AND that the cam belt was properly installed. It is spot-on correct. Timing is precise and correct to spec. When overhauling the carb I discovered the pin holding the choke linkage had come loose screwing up choke operation. I repaired it and all works perfectly. The only thing altered from original is the drop-down solenoid (anti-dieseling) was removed. When I fired it up it ran exactly as badly, unable to idle and backfiring on decel. Living in Colorado I MUST pass emissions so all that equipment needs to work. Can anybody suggest what next to check (there are a load of sensors yet to check) that might cause this condition? I did discover cylinders 2 and 3 are oily (on plugs). Possibly stuck rings or valve guide seals? Please help! Thanks,
Don

Offline dave1987

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Re: 1978 Pinto backfire problem
« Reply #1 on: October 11, 2011, 09:22:02 PM »
Might you have a deceleration valve? It is mounted on the base of the intake manifold and sticks out towards the firewall. One single backfire will burn the valve diaphragm making it completely useless and causing a vacuum leak.

I don't know of anyone who reproduces them though. I would think you might be able to take it off and plug it, the cap off the vacuum line.

Back when I had to get my 78 tested, I had it passing WITHOUT the EGR valve or plumbing, and even with the catalytic converter hollowed out. It was rebuilt shortly before, but still...
1978 Ford Pinto Sedan - Family owned since new

Remembering Jeff Fitcher with every drive in my 78 Sedan.

I am a Pinto Surgeon. Fixing problems and giving Pintos a chance to live again is more than a hobby, it's a passion!

Offline ToniJ1960

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Re: 1978 Pinto backfire problem
« Reply #2 on: October 12, 2011, 03:37:44 AM »
 Mine did that years ago,I took it to be checked and they said it was the dump valve, that goes to the air pump and the exhaust manifold. They cut a hole in the vacuum hose to it and it quit, I just took it out and blocked off that vacuum port.

 It backfired at every stop sign on my way home from work until I had it checked.

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #3 on: October 12, 2011, 09:18:10 AM »
Thank you very much for your input... I am still attempting to identify each little valve and sensor (it surprises me just how much more emission garbage appeared between my '74 Pinto wagon and the '78). I will verify that particular valve and remove it, once I am certain which it is. I will also verify the dump valve, and look into it. One more question... has there been a consistent problem with the Ford valve guide seals on this motor? I have read a lot of folks commenting the need to replace them as well as how-tos... I am afraid it might be my oily plugs problem, but I have to fit an adapter to use a compression gauge thanks to the 7-mile-deep and narrow plug placement!

I will keep you posted as to what I discover... what I do not like is what is causing the backfire, even if the decel valve may be blown regardless...

RSM

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Re: 1978 Pinto backfire problem
« Reply #4 on: October 12, 2011, 04:17:59 PM »
 Usually when valve stem seals go bad the oil goes past the guides and into the combustion chamber where the oil is mixed with the fuel and it gets burned...hence blue smoke but that will show up as carbon on the plug. With enough oil being burned the plug may foul and since the oil isn't being burned it settles on the plug and shows oily. An oily plug may also indicate that the rings are the issue. When oil comes past the rings it's not mixed with the fuel as much as coming past a guide. The oil still settles on the plug and can foul it or lessen its ability to properly burn the fuel/air mixture. A compression test will tell you a lot.

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #5 on: October 13, 2011, 10:38:45 AM »
Thank you all for your help! For the sake of clarity, please see the attached diagram, and my questions are-- Is the "dump valve" identified as number 9B289 (circled in the illustration), and is the "deceleration valve" identified as number 9D473 (also circled in the illustration)?? I have not had time to do the compression test yet, that is next. I did managed to remove, test and clean the EGR valve. The diaphragm works perfectly, but the gasket had dissolved and vanished, not that it mattered, as the manifold chamber was blocked 100 percent by carbon buildup. I carefully decarbonized it and have a new gasket to install. It is now cleaned thoroughly and ready to reinstall. I doubt it will help running very much but it cannot hurt! With 52,000 original miles it is difficult for me to imagine the motor requires substantial work done to it. Please let me know about the valves. Thank you!
Don

Offline ToniJ1960

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Re: 1978 Pinto backfire problem
« Reply #6 on: October 13, 2011, 03:08:15 PM »
 Thats the dump valve, at least that was the name they gave it when I had it `fixed`. Im not sure what the two vacuum hoses are for it, I guess one is a control signal from a switch in the air cleaner I cant remember anymore.

 The other one you show looks like a ported vacuum switch that goes into that piece in the intake maifold. Im going to get my Chiltons out and look,but Im pretty sure the decel valve is mounted right at the carb. I might be wrong. Im not even sure they all had one mine doesnt. But like many other things it may have been removed over the years.

Offline ToniJ1960

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Re: 1978 Pinto backfire problem
« Reply #7 on: October 13, 2011, 03:14:34 PM »
 Attached to the intake manifold. A hose connects it to the carb

 But, "Use of the deceleration valve on the Pinto/Bobcat was discontinued after the 1977 model year"

Offline D.R.Ball

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Re: 1978 Pinto backfire problem
« Reply #8 on: October 14, 2011, 01:45:21 AM »
The anti back fire valve is what you should have....It's name should be clear...It stops the back firing........ .You can find them on any Ford with a 2.3 except the Turbo Engines....The y do not need one...

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #9 on: October 14, 2011, 08:39:00 AM »
Again, thank you for the suggestions and insight. I finally managed to successfully accomplish a compression test... unsurprisingly, all cylinders have 130 lbs very evenly, and that with a questionable seal on the compression gauge, so I am not too concerned about any internal engine traumas. I will indeed check the various devices starting with disconnecting the divertor valve (a.k.a. dump valve, blow-off or bypass valve, anti-dieseling valve, etc) and see how it runs. I will consider doing a reseal on the valve guide seals before long, but really should drive the car a bit first, to help loosen any gumming up, as it suffers mostly from both sitting and aged seals/rubber parts. BTW- you are correct, there is no "deceleration valve" on my 78. There is a vacuum valve (as circled on the above diagram) on the intake manifold, but that is it besides a load of vacuum connections and devices all sprouting from the air cleaner.

On another note, did Ford use the same "faceplate" for their AM/8-track radio as for the standard AM radio?
Thanks to everybody once again! I will post when I track down the problem.

Offline D.R.Ball

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Re: 1978 Pinto backfire problem
« Reply #10 on: October 14, 2011, 09:20:00 PM »
I have a 1976 Pinto if you need pictures of what the vacuum lines look like... Your carb may have more lines but the anti backfire system did not change.......

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #11 on: November 01, 2011, 10:25:00 AM »
Brand new Anti-backfire valve, brand new vacuum temp control valve, brand new canister valve, brand new handful of other valves going to and from the distributor and vacuum lines. EGR cleaned and tested. It is flawless. Even with the air pump disconnected it stumbles and backfires miserably. Bear in mind the carb was carefully cleaned and overhauled, and all functionality restored. Some previous owner has definitely messed with the catalytic convertor, and as noisy as the exhaust sounds (with a correct, new factory-muffler) I am thinking the Catalytic convertor may be a shell, so to replace the needed back pressure and operational ability I will get a new, correct unit. As, in respect to emission garbage, one MUST either have ALL (working) or NONE... half-assed does NOT work... I am wondering, could the ignition box be going south to cause stumbling and backfires? I am running out of valid possibilities, and quite frustrated.

Offline D.R.Ball

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Re: 1978 Pinto backfire problem
« Reply #12 on: November 02, 2011, 04:31:21 PM »
Have you checked the vacuum advance on the distributor... ...Just a thought, my car is having some of the same issues and I when I went over the owners log book for the car it said it had a problem with the timing IE the vacuum would not advance the timing based on r.pm. changes...Of which leads me to believe that the vacuum advance has failed....

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #13 on: November 02, 2011, 09:15:47 PM »
Thank you for the excellent suggestion. I did check the vacuum advance as well as timing and both seem to be working correctly. I have not been able to test the ignition module as we are now on an every-three-day 14" snowstorm routine... please, Lord, not another fall/winter like two years ago!!

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #14 on: November 08, 2011, 10:15:07 AM »
Quick update: the ignition module is perfect, no problems. I am running low on possibilities! Thanks to all for your suggestions!

Offline sedandelivery

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Re: 1978 Pinto backfire problem
« Reply #15 on: November 08, 2011, 04:16:12 PM »
Is your EGR valve working properly?

Offline D.R.Ball

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Re: 1978 Pinto backfire problem
« Reply #16 on: November 08, 2011, 07:56:40 PM »
How did you test the vacuum advance, with a vacuum source like a mity-vac ? Or just disconnect it......Also I just got done changing the spark plugs and spark plug wires and can say it's a lot better, not perfect but a lot faster, more power etc......Have you checked the routing of the wires if it's not right it could cause some timing issues like a cross fire in the firing order....

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #17 on: November 09, 2011, 11:24:35 AM »
I checked the vacuum advance while checking timing with a timing light... it seemed fairly obvious when disconnected. I routed the new wires and plugs carefully, so although I can never be entirely able to disqualify them, it seems unlikely. Thank you!

RSM

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Re: 1978 Pinto backfire problem
« Reply #18 on: November 09, 2011, 04:45:23 PM »
Is the car still backfiring when you decelerate or has it changed? Seems like your saying it backfires all the time..maybe it's just how I'm reading it. Does the engine diesel sometimes when you shut it off?

Offline ToniJ1960

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Re: 1978 Pinto backfire problem
« Reply #19 on: November 09, 2011, 08:15:25 PM »
 I reread and reread but it doesnt really say anywhere,is it backfiring out of the exhaust or the carburetor. If youve done everything you said already it might be time to start back at the beginning.

RSM

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Re: 1978 Pinto backfire problem
« Reply #20 on: November 09, 2011, 10:11:52 PM »
Car ran OK, but no idle and backfiring on deceleration. (This is what he said in the first post) Even with the air pump disconnected it stumbles and backfires miserably. (This comment is made later)...Kinda confusing  as to when it really does backfire.

Offline ToniJ1960

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Re: 1978 Pinto backfire problem
« Reply #21 on: November 10, 2011, 01:56:58 AM »
 Think it could be a burned or sticking valve or weak valve spring? Doesnt say a compression test was done might be a good idea, like I said maybe start at the beginning.

RSM

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Re: 1978 Pinto backfire problem
« Reply #22 on: November 10, 2011, 06:48:36 AM »
I finally managed to successfully accomplish a compression test... unsurprisingly, all cylinders have 130 lbs very evenly, and that with a questionable seal on the compression gauge, so I am not too concerned about any internal engine traumas....he did a compression test and it looks good as far as that goes. Sticking valve is what I'm starting to think...or something along those lines. If it were a burnt valve the compression would be down on that cylinder.

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #23 on: November 10, 2011, 04:22:10 PM »
Quick clarification: EGR is cleaned and working perfectly. Compression test was indeed accomplished and it was even and good in all cylinders, but I cannot guarantee a perfect seal on the gauge, so will retest now I have a good gauge. The car seems to be backfiring in the exhaust, what some refer "more accurately" as "after fire". It does not backfire through the carb. It does not smoke or make mechanical noise in the motor, like a valve problem would. I am going to revisit the vacuum advance on the distributer despite all indications it is working correctly. It is possible the carb needs readjusting since rebuild, but still should not be a major cause. My friend has an analyzer and I will plug that in as opportunity permits. Right now, I am seriously looking at the catalytic converter... the more I read, the more it may be contributing to my problem...

RSM

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Re: 1978 Pinto backfire problem
« Reply #24 on: November 10, 2011, 05:46:00 PM »
So this happens when you let off of the accelerator slowing down...correct?

Offline D.R.Ball

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Re: 1978 Pinto backfire problem
« Reply #25 on: November 11, 2011, 02:25:51 PM »
Where have you set the timing, as per the emissions sticker ? If so try to advance it a couple of degrees, like to 6 if its a 2 degrees because the original owner has had a similar problem and this helped fix it.On my car...

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #26 on: November 14, 2011, 12:02:12 PM »
Given our elevation, that may be a wise idea... yes, the timing is currently set precisely to the emission sticker settings... your suggestion is great, thank you, I will see what it does.

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #27 on: November 14, 2011, 12:07:26 PM »
So this happens when you let off of the accelerator slowing down...correct?
When I step on the accelerator, the engine revs perfectly fine, and as it comes back down, it "backfires" in the exhaust, on deceleration. I have not had time to test it, but ever since I drove the car home,the exhaust has always seemed louder than it should, even with a correct muffler installed, so I still suspect the catalytic converter to be empty. I have a new one ready to install, as time permits.

Offline 74WagonMeadowGreen

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Re: 1978 Pinto backfire problem
« Reply #28 on: November 14, 2011, 12:09:47 PM »
Is your EGR valve working properly?
EGR and passagewayis cleaned and tested, works perfectly.

Offline pintogirl

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Re: 1978 Pinto backfire problem
« Reply #29 on: November 14, 2011, 12:21:04 PM »
I know this is not a Pinto I am going to be writing about, but I thought I'd mention it anyway. I am haviing a problem with backfiring when decelerating on my bus. One of the guy's an the Samba said that it is possibly caused by an exhaust leak. He told me to check all my doughnuts and gaskets on my muffler.

Could this possibly be the same senario for a Pinto? Maybe the exhaust system has an air leak?
Kim
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I have come to realize that I am powerless to cuteness of a rusty old Pinto.

Sacramento CA