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mike88
New User
Feb 26, 2008, 6:39 PM
Post #1 of 7
(2811 views)
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1976 Ford Van won't idle
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I have a 1976 Ford E150 van. 351w 2bbl, auto, standard breakerless ignition. It ran great until a couple of weeks ago when it started running rough, especially at idle, then it got better and ran ok, then worse and now it won't idle at all. Plugs are fairly new and look fine. I pulled carb and looked in float bowl, very clean. Carb was rebuilt 5 years ago. I thought it was bad gas so I ran it off a gas can with fresh gas, no improvement. Van has been very well maintained and has about 145k miles. Any ideas?
Thanks alot, Mike
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 26, 2008, 8:23 PM
Post #2 of 7
(2806 views)
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Re: 1976 Ford Van won't idle
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Some ideas: Vacuum leaks - even check out brake booster and line. Spray carb cleaner at EGR, intake manifold, vacuum lines, carb base etc - carefully as hot spots could flash. Change in idle for better or worse doing that marks a trouble spot.
EGR pintle may be dirty - try cleaning it off vehicle. Check timing chain lash. Can be done looking at dist rotor and turning crank with socket back and forth - no more than 5 degrees allowed and if an original the plastic cam gear is toast from age alone.
Distributor bearing wear possible. Sometimes you can tell with a dwell tach at different speeds dwell reading may flutuate wildly - disregard the dwell # just the fluctuation.
Set fast idle cam on first step so it can stay running and pull or cancel one plug at a time for even RPM drop. Check out any cylinder not like the others.
Does it smooth out under moderate load?
Lots of possibilities so just start checking what you can,
T
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mike88
New User
Feb 26, 2008, 10:32 PM
Post #3 of 7
(2804 views)
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Re: 1976 Ford Van won't idle
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Thanks for quick reply. I checked for vacuum leaks already except for booster. I will check that in morning. This van only has pcv valve, no EGR. I replaced timing chain 10.000 miles ago. Distributor seems tight. Oil has been changed every 3000 miles since new. I think it smoothed out a little under load. Again this problem is intermittent. IT was almost back to normal before it got really bad.
Mike
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 27, 2008, 5:44 AM
Post #4 of 7
(2802 views)
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Re: 1976 Ford Van won't idle
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For the booster, just plug it off at the source and see how it behaves - duh - you won't have power brakes for that test so use judgement.
Vacuum testing could be real helpful and the canceling of plugs one at a time.
What I was looking for with asking if it smoothed out with load is if this is vacuum or intake related at all AND then the carb under load goes off of idle mixtures to intermediate and on to WOT mode. Sometimes cleaning out thru the idle mix screws can help - just put those back where they were.
EGRs can crust up. Hard to just know by looking at them and unplugging the vacuum line isn't the test. You should be able to stall it by hand by pulling up on the diaphragm. If you can get it clean - off vehicle - then just plugging the vaccum line takes it out of the diag for now.
Valve springs have been an issue for me and elusive to target. Weak or cracked ones may idle ok, compression test ok but lose it under load. Vacuum test and watch the needle bounce at various loads is very informative - a lost tool for diagnosis that was key in my day. The tool never far was a pistol type vacuum pump and gauge I wore out a couple times for all kinds of tests and uses. I'll post a pic of one if I can find it - great thing to own in any tool collection.
For now test what you can and try to figure if this is a general roughness or if selecting a cylinder or two. You can swap plugs and wires if a cylinder is isolated to see if problems follow cylinder or parts.
Any other clues? Behaviors when cold, hot, wet, load etc?
T
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 27, 2008, 5:53 AM
Post #5 of 7
(2801 views)
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Hand Operated Vacuum Pump Kit
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Found one! This was for sale on the web but it's exactly what I'm talking about. This has the "T" the pencil head and a check valve to put in line with the gauge. Handy tool for tons of things. Now I need to find, scan or write just how to use it for engine problem diagnosis!
T
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mike88
New User
Feb 27, 2008, 2:09 PM
Post #6 of 7
(2797 views)
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Re: Hand Operated Vacuum Pump Kit
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I have a vacuum pump. Its the plastic version but it works ok. Checked the booster and line, no leaks. Also the vac. advance on dist. and vacuum line to trans, all good. Hooked up vac gauge to intake. Its steady at about 17 psi at 1500 rpm, below that it really starts to miss and die. Seems to run ok at higher rpm (2500+) and when I accelerate. I ran out off carb cleaner so I have to run into town (I'm on Big Island in Hawaii) I will try your idle screw hole idea next.
Thanks again, Mike
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mike88
New User
Feb 27, 2008, 9:01 PM
Post #7 of 7
(2790 views)
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Re: Hand Operated Vacuum Pump Kit
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Tried spraying idle screws holes with carb cleaner, no help. I noticed one more vacuum line going to choke pull-off, I checked pull-off diaphram with vac pump, it was bad so I capped off the fitting at carb base. This helped alot! It now will idle at about 900 rpm, but still rough, below that it dies. I tried pulling plug wires one at time. It was equally rough on each cylinder. I drove it. Its smooth under load and has lots of power. Any more Ideas? At least its drivable now. thanks for your help.
Mike
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