Diagnosis Help (hard to idle)

Hey folks, it will be a few days before I get the chance to really try and work this out so I thought Id ask for some advice here in the meantime.

My lovely wife took the van to the store yesterday and told me when she started it up to come home it wouldn't idle (it would just drop right off and quit). I checked it when she got home and that was indeed the case, you had to stay feathering the gas pedal to keep it running.

I turned the idle screw up probably a full turn to keep it idling and then checked the timing, it "appeared" to be a good 5 degrees off so I set it back to 5btdc. Note that the scorch marks inside the distrib cap appeared to be right where they should be though so whatever happened occurred on this run to the grocery. It's idling ok now but it will occasionally backfire through the carb when you rev it up (which I know is a definite sign of something gone awry).

The last major change I made was several months ago when I put on an OEM re-manufactured carb (OEM carter BBD) and a new distributor, been running great since then. This weekend I plan on going through the motions of a tuneup first thing, resetting the timing and idle, checking points etc. If I don't sort it out that way I have my original carter BBD already rebuilt and waiting on the shelf, I plan on swapping carb (a 20 minute job) to rule out any carb related issues. If the carb swap doesnt fix it I know it's in the ignition somewhere.

Anyone got any quick idea's as to what might have gone wrong to cause the idle to drop so far so quickly?

If it's still got points sounds like the dwell is off this will affect timing as well.
You say you replaced the distributor there may have been no cam lube
and the points may have worn prematurely this would be my guess!
Not sure what you mean by "scorch marks"?

Hey!!= Ist - dont swap out the carb =till u have done a complete tuneup- do not use those saved"maybe good? ) parts=we all have them - get new- plugs, wires-yes=wires!! cap rotor, condenser, and points- set points with a dwell meter also. Then run it & see how all is & adjust- one (1) thing at a time. If all is great = then ??maybe ?? put that carb on.=Yes=that all costs a few bucks =yet then you will know where you stand!! also - actually 1st= check for a Vacumn line off - = symptoms you describe = will give no / bad idle

Mr. John wrote:If it's still got points sounds like the dwell is off this will affect timing as well.
You say you replaced the distributor there may have been no cam lube
and the points may have worn prematurely this would be my guess!
Not sure what you mean by "scorch marks"?

"scorch marks" a distributor cap that's been on awhile will have marks on the contacts where the rotor fires as it passes.

Twinpilot001 wrote:Hey!!= Ist - dont swap out the carb =till u have done a complete tuneup- do not use those saved"maybe good? ) parts=we all have them - get new- plugs, wires-yes=wires!! cap rotor, condenser, and points- set points with a dwell meter also. Then run it & see how all is & adjust- one (1) thing at a time. If all is great = then ??maybe ?? put that carb on.=Yes=that all costs a few bucks =yet then you will know where you stand!! also - actually 1st= check for a Vacumn line off - = symptoms you describe = will give no / bad idle

Hmm, I thought about vacuum as well but there's only one line on the motor , it might have sprung a vacuum leak some other way though. I wont get a good look at it until i can break down the doghouse this weekend.

After looking it over really well I suspected the idle circuit in the carb more than anything else. It's a ten minute job and I have a freshly rebuilt spare so I swapped them out, set the idle and timing at 5BTDC and it runs great. That "new" factory rebuilt carb I ordered from Summit (Carter/Holley BBD) never ran right from the day I put it on, I'm going to see if they will exchange it, if not I'll get a kit and rebuild it myself.

I don't know if a 273 thing or what, but the I have in the '67 van is very picky when it somes to carbs. I rebuilt the carb that came on it and still had troubles with it. So I did the carb swap with my '68 318 and things are perfect. I'm glad you mentioned the summit carb, I was thinking about getting one and decided to go back to guaranteed carbs where I got the one for my '68, they have a lifetime warranty program.

You guys talking about carbs. Our gas stations are going to run with 15% ethanol now, what do you see around you? And have you seen any problems from your carbs yet?

67a 100 pickup wrote:I don't know if a 273 thing or what, but the I have in the '67 van is very picky when it somes to carbs. I rebuilt the carb that came on it and still had troubles with it. So I did the carb swap with my '68 318 and things are perfect. I'm glad you mentioned the summit carb, I was thinking about getting one and decided to go back to guaranteed carbs where I got the one for my '68, they have a lifetime warranty program.

Yep, my 273 is picky as well. The original 45 year old carter BBD ran great but needed a rebuild. I ordered a direct replacement Carter BBD (now owned by Holley) through summit and it ran completely different, and not in a good way. I never could get it to idle right where I wanted it, it was always too high or too low, and it has an insane amount of vacuum on the vacuum advance port compared to the OEM one. I think something is goofed internally, it definitely isn't piped the same way inside based on how it acts. I got the carb from Summit about six months ago, if they wont exchange it I'll call Holley and see if they will.

I have run a Holley 2280 2BBL on it as well (same "small Rochester" bolt pattern) and it did run very well but it needed a rebuild too. I need to rebuild the 2280 and keep it as a spare. On a side note, I dont think Holley calls them "2280's" anymore but you can find them on Summit by looking at the picts or call Holley and ask them what the new PN is.

Stoopid john wrote:You guys talking about carbs. Our gas stations are going to run with 15% ethanol now, what do you see around you? And have you seen any problems from your carbs yet?

We are running 10% around here at the moment. I have to be very careful in regards to heat management or I risk boiling the carb off on hot days, I'm sure 15% ethanol wont help that boiling point any.

Ok, turns out I may have been wrong about the idle circuit.

I was coming home from the car show yesterday and it all of a sudden started sputtering and carrying on like the timing was off way off. I goofed with it for a couple hours in the parking lot checking points, wires etc while I waited for my ride.

I eventually got my spare carb and went back and swapped that out with no good results (just eliminating the carb as a source of trouble). All of a sudden it started right up and ran normally so I took off for the house, and got about a mile before it happened again.

Here's the interesting part, I noticed that when i get moving the ALT meter is pegged to the right right before it starts acting up. I went over to the parts store and got a new coil figuring mine was cooked. After the coil swap I was able to get it home but the ALT meter was still pegged to the right going down the road.

So combine that and the sweating battery and something isn't right, I'll change the volt regulator today but I don't think that's it. Is there anything built into the alternator that may stick and cause this thing to over charge? Anything else that might make it charge full bore all the time?

I'm going to carry the battery to get tested today.

Good - verify batt is good in all cells-then when u get it installed- disconnect the alternatot wires - cover them so wont short out & start the engine - hows it run?? if good then - disconnect the regulator - rehook the alt & retest- any diff?? bet its the battery- maybe subsitute a know good batt some buddy has ?

Alt pegged to the right is full charge. This will happen when the battery is completely dead (not in your case if it starts) of if the regulator can't 'see' the battery (a bad wire or connection, most likely) or if the regulator is the OE point style and the points have welded together.
Considering all your other recent wiring issues, I'd say it's time to rewire!!!
It will be some time and money, but the ol van is trying to tell you it needs help and it hasn't burned down yet.

thanks for the advice guys.

I did some testing this morning. The van started right up with no trouble and ran fine, 14.4 volts at high idle and 13.2v at idle (normal). My wife told me (this morning) the ALT gauge was pegged when she had it start cutting out last week.

I just took the battery to the parts store and it tested fine as well. It also has a solid state VR in it and Ive tested it with a spare SS VR that I have on hand and there's no difference there.

So, it seems that "occasionally" for reasons unknown the van will decide to start charging at max capacity which sweats the battery and eventually cooks the coil. The coil going bad is what makes it start running like its jumped time. I don't know what makes it start overcharging and I don't know what makes it stop!

I think, like Rod recommended, I'm going to have to trace all the wires out in the charging circuit (including block/frame grounds) and replace them with new stock, checking connections along the way. Not looking forward to that ):

The plot thickens.

My wife said she left the electric fan running (and turned the van off) and left it for 30 minutes or so last weekend, the van smelled "funny" (Id guess burning electrical) when she got back in it and then it started acting up. Might be related, might not, but now Ive got to check all the terminations and wires in the charging circuit.