1974 Valiant Scamp, timing retarding when revved

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elementaltoad

elementaltoad

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I have a strange issue I don't recall seeing on any other car before. This is a 1974 Valiant Scamp with the 318, when I got the car it was running rough at idle and stumbles horribly while accelerating in gear. The first thing I did was check timing and fueling which lead me to a strange timing issue. While taking a look at the timing with the vacuum line plugged, I noticed that the timing was constantly retarding as it gained RPM.

Base timing seems to be set right around 5*, which seems a bit low, but it starts easily. However, with the timing light on and steadily increasing RPM the timing will drop from 5* all the way past -10* while running consistently worse until I can't see the timing mark at all.

Has anyone experienced this before, and what would be the first things to check. It appears that the stock ignition system is in place, and it has not been modified or converted.
 
Sounds weird. First check, pop distributor cap, see if rotor can be twisted about 10 degrees CW, and it returns. Second test apply mityvac to vacuum advance pod, apply vacuum see If advance plate moves, and returns when vacuum is released. Then set engine at 5 deg mark, and observe if trailing edge of reluctor tooth is alligned with pickup sensor.

If you have not found a problem, put things back, T mityvac inline with vacuum advance, start engine, vac should be near zero with carb at idle, vacuum increase off idle.

Also check coil, see if blue wire goes to coil+, and green wire on coil- and no other connection there.

Also if using clamp on timing light make sure clamp polarity is correct, if setback light, set to zero, or try different light.
 
And if it persists or if the timing lite shows dropped sparks, swap the clamp over to #6. If same going on here then I would reverse the polarity on the pick-up coil. I have seen that a few times.
I made my boss $1500 on a motorbike once, that was doing this.It seems several other techs had worked on this bike and had changed about everything electrical that could be changed to no success. Well unbeknownst to me, the customer and my boss haggled out a deal for $1500 if I could fix it. It was doing the same thing as your car, but I didn't know it yet. It would only rev to about 3500rpm and then it hit a wall, running progressively worse as it got there, kindof like it was running out of fuel. When I sawed on the throttle sometimes the Rs would take off like normal. Well if you know anything about motorcycle CV carbs this is almost a sure sign that there is something wrong with the carbs.So I went and asked my boss "Anybody have the carbs apart?"to which he replied yes a couple of other techs had had them apart and couldn't find anything wrong. So I pushed it into a corner (this was winter work), and carried on with other things and let my brain mull it over.Did you know that the brain can figure out stuff even at times when you are not in charge of it? Well, mine does anyway.
Well a couple of weeks go by, and the idea comes to me to put a timing lite on it and low and behold, the timing is going backwards, and forwards, and dropping sparks, and just generally misbehaving. So I go ask my boss, "anybody been working on the electrical?" to which he replied yes. In fact the entire wiring harness had been changed and every sensor on it.And the EFI computer too.Ok I said and pushed it back in the corner, and continued with other projects.
Well a few more weeks go by, and one day a memory comes to me. A couple of years earlier I had a pick-up coil fail on me in my FormulaS. After I replaced it with a good used one (from the glovebox where I used to carry spare electrical stuff), I fired it up and set the idle timing, and like a good little boyscout I went to check the power-timing and there it was; all this misbehaving.Well after a lil headscratching I got the idea to reverse the polarity of that pick-up coil and presto, back in action. I had forgotten this little nugget. But my brain had obviously filed it somewhere.
So this God given miracle of creation,brain of mine,hauls out this memory and parks it a lil closer to where I can see it. Well I said stranger things have happened.
So I ask my boss," has this here sensor been changed", to which he replied that he'd have to call and find out. So I push it back in the corner, and go back to other projects; winter work in a small community is like that. In order to not have to lay me off for lack of work, my boss used to bring in winter work at a much discounted rate. It was my idea actually but that's another story.
So a few weeks go by, and the answer comes back; yes all the sensors were changed and this particular one more than once. Ok I said, and return to my work area.So now it's getting close to spring, and my boss still has not told me about the deal.
So now I got nothing to lose. That memory is prodding me. So I pull that mean machine out from it's resting place, blow off the dust, and pull up a chair and a wire stripper. A few minutes later, I hit the key, and it springs to life same as usual.So I let it idle to warm up and carry on my business, I got other projects on the go, don't you know.
Well after a while I come back to it and roll into the throttle a bit, not knowing exactly what to expect. But Huh, it takes the throttle, so I twist it a bit more and Huh,it takes that too. So I put the light on it and sure enough the computer is advancing it exactly as it is supposed to! Nice work!
So I get to sawing on the throttle, cuz I know the boss is around and he's getting anxious to see this thing out the door,and he knows the sound of this old girl.But he knows how I work, so he's being patient(we have by this time, about 20 years of time spent together). So all of a sudden he comes bursting into the shop, to see what the heck I'm doing, and finds me sawing on the throttle and the engine is responding as if nothing had ever been wrong with it.
Well that guy is beaming.
Now he tells me the backstory.
I finish the repair with solder and shrink tube,polish up the bike and finalize my time spent. He gives me a pat on the back.
Life is good.Spring is here.
 
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Guys, I really appreciate the input! Well, a bit more background and some results:

This is a ATK 318 motor (DD03), stock replacement as far as I know. 20k miles on it.
It has an Edelbrock 4BBL carb on it, Edelbrock Performer intake.

Distributor cap, rotor, and wires are all fine. Rotor can be turned slightly and returns as it should, advance plate moves, swapped coil wires, installed new fuel filter and filled up with fresh 93. None of this resolved the issue, I rechecked with the timing light on both #1 and #6, at idle timing is 5* advanced, if I open the throttle and hold it by hand a bit progressively more and more, timing continues to retard until I can't see it on the timing tab. It really sounds like it has a giant cam in it, and revs very freely, it almost feels like a gunked up carb needing a rebuild but the timing issue is throwing me for a loop. I'm admittedly more familiar with GM HEI set ups, and I'm very tempted to go ahead and put an HEI system in, I'd hate to ruin the original ignition system but it seems overly complicated.

I am going to order a rebuild kit and clean out the carb to be safe, it's a fun thing to do anyway. However, on the ignition I noticed a couple of things that look like they might be in poor shape, though I'm not certain what they do.

The ignition box here, or ECU as I've seen it called, I assume is similar to the HEI modules. It appears to have leaked its' guts on the fender, can these be bypassed or diagnosed to eliminate it as a potential issue?
15284071_1231594996900794_3906150863280305509_n.jpg


The Ignition coil has been....remote mounted by the previous owner, it also appears to have been rewired and has a purple and blue wire.
15284185_1231595003567460_5245394687463805462_n.jpg


The voltage regulator on the passenger fender appears to have also leaked its' guts, looks like some sort of dialectic fluid. Almost like dried tree sap.
15181176_1231595000234127_783242868668050350_n.jpg


I'll try to get a video of the way it runs tomorrow when my neighbors are less likely to stab me, but I am really interested to know more about the ignition system and how to bypass as much as possible for troubleshooting purposes if anyone knows more about this odd electronic ignition.

Thanks!
 
I think I may have found it, the pick up coil under the cap does not appear to be secured. It moves all over the place, it look like there is supposed to be a clip holding it in but I don't see it, anyone know where to get one, or have an alternative solution?
 
I have seen pop rivets late model, but can be tapped for I think 8-32 screw.
The ECU, is a dumb thing, it releases coil current when pickup signal goes positive after going negative and past zero. Zero happens when tooth is aligned to pickup nub. Then a bit past that, spark happens. The pickup signal increases voltage, with engine speed, so timing advances some. Maintaining gap is crucial, and runout and wear of advance components are problem areas. If it were not for point and rubbing block wear, and bounce, points just as good. Both use ballast resistor. Some convert to HEI, they have dwell, and current control, eliminating ballast. But, there will still be pickup issues. The exactness, is not good, but few know different, because it has always been that way.

So with loose pickup, you might be getting multiple triggers, and that looks as retarded timing. If the pickup has been hitting reluctor teeth, might be good plan to change both, and properly set gap using 0.008" brass feeler. There is top/bottom on reluctor, for SB vs BB, so install correctly.

I like Mallory uni-lite with vacuum advance. I also have developed a COP programable ignition, that works better. That is work in progress....
 
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I haven't been able to get to the bottom of the timing issue yet and feel like it may be partly due to a poorly set up carb. Once it warms up I can't put it in gear without stalling, got myself stuck in the middle of the road for a bit...that was fun. It is an Edelbrock 1406 with what look like plain colored springs. I can't read the jets or rods, but I'll try to get the numbers tomorrow. I ripped the carb off and started a rebuild since I don't know the history, but I do know it was not originally on this car. I also noticed the accelerator pump was set to the lowest hole, or weakest shot. I got a short video of the idle, which sounds horrible, and then the part throttle stumble (you can see the battery and motor shaking), as well as the lag in quick throttle transitions.

 
What are results of tests suggested in post #2? Have you fixed pickup sensor mount problem, and set gap?
 
Please.... or sorry..... but I have to ask to remove assumptions.... Is the mark going up the harmonic balancer or down????? Up towards the water pump would be correct. That would be advancing.
Motor sounds way off like you say, but it does sound like a good motor.
 
Advance appears counter clockwise change, retard is clock wise, as viewed from good timing light, observed facing ballancer. Since timing mark positions vary, on the LA engines, CW, CCW description works for all LA years.
 
Kit,

KitCarlson said:
Sounds weird. First check, pop distributor cap, see if rotor can be twisted about 10 degrees CW, and it returns. Second test apply mityvac to vacuum advance pod, apply vacuum see If advance plate moves, and returns when vacuum is released. Then set engine at 5 deg mark, and observe if trailing edge of reluctor tooth is alligned with pickup sensor.

Cap, rotor, and plug wires are all new. Rotor also returns as it should. The pickup is gapped and locked down, and it aligns with the timing properly.

If you have not found a problem, put things back, T mityvac inline with vacuum advance, start engine, vac should be near zero with carb at idle, vacuum increase off idle.

Vacuum advance holds fine, no leaks, couldn't find my actual vacuum gauge though (still unpacking boxes)

Also check coil, see if blue wire goes to coil+, and green wire on coil- and no other connection there.

Coil wiring was fine, I tried swapping it as well

Also if using clamp on timing light make sure clamp polarity is correct, if setback light, set to zero, or try different light.

This is a cheap light I inherited and was having fits getting a good ground. After I got the car running well enough to idle as it does in the video, it looks like timing is going the right direction CCW when revved, but it's intermittent. It seems to be following heat/how long it's been running. The stumble and idle get more erratic as it warms up.
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I also pulled the ballast connections apart last night, which was a bear without breaking it. They are heavily corroded and were starting to melt. If rebuilding the carb and cleaning up the ignition connections doesn't clear it up, I'll just pull the entire front harness and go through it for a reloom/rebuild.
 
As said, if the index-mark on the balancer, marches up (CCW from the front of the engine), and disappears under the waterpump, that would be normally advancing and is correct.
If the cooling fan is direct drive, or if the clutch is tight, I would repeat the test with the Cooling fan disabled, and with about 12* of idle timing.
It sounds like she needs more idle timing,more pumpshot,Less idle fuel, and I believe your T-port sync is off/ and or the metering rods are tardy.
But I have to agree, that if the timing mark is in fact retarding (marching CW, down, towards the power-steering pump), That the engine would sound like it does. And I know of no way that could happen; so the first thing I would do is swap out the ECU. I have never seen a wrong-way marching timing mark.So ........I'm arm-chairing it,........ again.
The vibratoryness kindof indicates to me that, if the fan/accessory drive is not the cause of it,I suppose the engine balance might be. That's a whole lotta shakin' goin' on.
 
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I just rebuilt the carb with the stock 98 and 95 jets last night, the tuning kit should be here tonight with the new springs. I will give the carb a try, set the timing, and fueling. I'll also take the fan off and try it, the shaking really is what bothers me. I hope it's the carb, but it wouldn't be the first time I had a harmonic balancer go bad either.
 
Looks like the ignition box is spewing its resin encasement out onto the fender, I think I'd address that...could be malfunctioning.
 
The two wires going to the distributor could be crossed.
 
MOPAROFFICIAL said:
Looks like the ignition box is spewing its resin encasement out onto the fender, I think I'd address that...could be malfunctioning.
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It looks like both the voltage regulator and ECU are doing that. I'll get some better pictures as I unwrap the electrical tape abyss that is the wiring harness. It's a marvel it didn't burn down before it made it to me....I even found wire nuts like you'd use for home electrical stuffed under the dash spliced into the radio/AC harness!
 
MOPAROFFICIAL said:
Rob, It would retard it 8-10 degrees , can't remember that it would advance backwards though....
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I'll check the wiring there too, but I seem to remember it had a specific way it plugged in. The other portion of the harness could be backwards though, that has been spliced at some point. The only time I had it idling well enough to try and get the base timing off it, it was at 5* retarded. It was originally a California car, maybe that was spec, but it seemed strangely low.
 
I installed the rebuilt carb and it runs much better. After that I set timing to 10* BTDC and idle speed picked up a LOT, I dropped the idle back down using the idle screw and then set the mixture for max vacuum, backing off a 1/4 turn. However, now when I put it in gear it stalls out. Restarts just fine and idles great, I think my problem is what I hear as a 700 RPM idle vs what it actually is, is different. I ordered a tach and it will be here tomorrow, should be a quick and easy installation. I quit for tonight so I don't bother the neighbors, but how do you guys normally go about tuning the initial timing without a tachometer? Just shoot for the most vacuum possible and then bring down the idle using the set screw?

As far as I got tonight, I was only able to get about 16-17" of vacuum at idle, what does a stock 318 normally get? That seemed a bit low to me.
 
check out the T-port sync in my sig below. Press on the little Mopar M. No I have no idea how it got there, that M just appeared as I was typing.
If you cannot see it, you may have turned this feature off. In which case go to the search function and type in AJ's and a selection will pop up.
 
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Pics of the dist. w/o air cleaner please, close-up.
 
AJ, I went and bought a timing light with the RPM function, super handy for this! The timed vacuum port has no vacuum on it at idle. Spark is solid at 10* advanced at 750RPM idle, 16" of vacuum, with or without the vacuum can plugged in. I then set the mixture screws to get the best idle, dropping the idle screw down to maintain 750RPM.

The biggest thing I noticed is the stalling issue when put in gear, and I am still waiting on the Edelbrock tuning kit to get here, but if the springs are too strong, it would dump a ton of fuel off idle transitions and going into gear when the vacuum drops correct?

Killer, I'll get a pic of the dizzy here in a bit.
 
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