318 Retards Under Load?

-
318duster73

318duster73

The OTHER village idiot
Joined
May 2, 2012
Messages
39
Reaction score
1
Location
Mary Esther, Fl
Ok, this started after I filled up at a little country store in the middle of nowhere, back in mid January. A week later, I started ripping apart the motor, and everything looked just fine. Upgraded the ignition box, did some other stuff, started her up today, and it still falls flat.

Basically, under load, the motor retards, it feels like putting it in 4th from a dead stop, but if you let off and then punch it, it picks up, then falls off again. Has anyone come across anything like this before? I don't mind replacing bad parts, but it seems like a waste to try shotgunning parts, hoping for a fix. I thought about water in the fuel, dumped in some alcohol, no effect. Maybe the fuel pump is on its way out?

Thanks, Alex
 
If it all started after getting the gas I would think water too, it sure sounds like it from your description. Pull your fuel line off the carb (with the engine cold) and unhook your coil wire from the coil so the engine won't fire and carefully try and pump a little gas into a glass jar and let it sit. If there is water it will settle to the bottom and the gas will set on top, easily visible.


Or you can try siphoning some out of the tank, whichever you feel more comfortable with.

***Be careful doing this as sparks and gas don't mix well in unintended circumstances.***
 
sounds more like trash in the fuel to me...try some seafoam,...could be that lil sock thing inside tank on end of pick up too...good luck
 
How about replacing the fuel filter? Blow the old one out over a paper towel to see if it was crudded up.

What condition is your fuel line in? Replace any sections of rubber. Make sure to check where the chassis line connects to the tank as well.

How are your float levels?
 
C130 Chief said:
What condition is your fuel line in? Replace any sections of rubber. Make sure to check where the chassis line connects to the tank as well.
Click to expand...

That's something to check if you didn't replace the rubber line by the tank. It could be collapsing.
 
I'll check on that line when I get home, too. Floats, lines, any easy way to check fuel pump pressure without a gauge? Mine got jacked and taken to Japan...
 
1st place I'd look is the gas. Pull the fuel line off & take a clean glass bottle & fill the bottle 2/3-3/4 way up while cranking the engine(it helps to have a partner do th cranking so you can watch the bottle) & then let it sit & settle. Any water or contamination should separate in the bottle. Important: DO NOT USE A PLASTIC BOTTLE since the gas could disolve the plastic & risk leaks &/or a false sample. Take a smell of it too. Make sure it doesn't smell like diesel fuel or kerosene. If the gas is ok check your fuel pressure & volume. Next look at the ignition system- cap, rotor, plugs & coil. Try to be systematic in your work & not just start throwing parts at it. Keep us posted on your progress.
 
My guess is a clogged fuel filter. If you changed one, look for another. There might be a stone type filter in the carb to check as well.

Jack
 
318duster73 said:
Ok, this started after I filled up at a little country store in the middle of nowhere, back in mid January. A week later, I started ripping apart the motor, and everything looked just fine. Upgraded the ignition box, did some other stuff, started her up today, and it still falls flat.

Why did you tear apart the motor ? Was it due to falling on its face ? Did you replace the distributor ? Did you do a compression check before tearing into it? Seems like there could be a lot of variables introduced. Hows the timing curve look? Are you positive the vacuum advance is hooked to a timed port on the carb and not a manifold vacuum port. To me it sounds more like an ignition issue. Do you still have the same gas in the tank you filled in january ? Just trying to place some thoughts and bring out some more info. Especially with the engine picking up when you let off, that increases manifold vacuum which could be pulling the advance and when you punch it the vacuum drops off.
Click to expand...
 
Looks like the gas is alright, at least, there's no water separation. Vacuum is on the timed port, still (passenger side of an Eddy 1406). Once I find a T fitting, I'll throw in another fuel pressure gauge. Replaced the rubber line at the tank, it looked alright.

The big reason I tore into the motor was the fact that whoever put it together last time used some really crappy hardware, seals, and componentry, not to mention the wiring horror I sorted out, it was already in the plans when this oddball problem came up. I figured that if tearing it down didn't make it disappear, I'd figure it out after.

Didn't replace the distributor, I'll take a look at the timing tonight. It seemed like a fuel deal to me, as letting off doesn't make it pick up, but getting on the accelerator pump does - but the regular fuel flow seems ok, just going by the inline fuel filter.
 
I don't think this is really your problem, but if the car bottomed out or something it may have a restricted exhaust. I say this only because it reminds me a lot of how cars act with plugged converters. Air filters can plug and do this too. I think you have a fuel problem though. Take the line off the carb and extend it enough to be away from the engine. Put the line end in a gallon jug, and let it idle till the bowl runs dry. If you don't get a half gallon or more you may have a fuel delivery problem.
 
You need to get a flow test on the fuel pump! It should pump a minimum of 1 quart or better in 1 minute @ idle.
You should do this test at the connection where it goes into the carb so as to check all lines and the filter.

Like magnumdart just posted!
 
Lonewolf3165 said:
1st place I'd look is the gas. Pull the fuel line off & take a clean glass bottle & fill the bottle 2/3-3/4 way up while cranking the engine(it helps to have a partner do th cranking so you can watch the bottle) & then let it sit & settle. Any water or contamination should separate in the bottle. Important: DO NOT USE A PLASTIC BOTTLE since the gas could disolve the plastic & risk leaks &/or a false sample. Take a smell of it too. Make sure it doesn't smell like diesel fuel or kerosene. If the gas is ok check your fuel pressure & volume. Next look at the ignition system- cap, rotor, plugs & coil. Try to be systematic in your work & not just start throwing parts at it. Keep us posted on your progress.
Click to expand...


That's what I would do!!! Or should I say would have done.

How long did you let it set? It doesn't happen instantly.
 
I've had spark plugs go bad where they'll idle, but under load the spark breaks down. And no amount of cleaning them would fix it. (they looked brand new)
 
Valvebounce said:
I've had spark plugs go bad where they'll idle, but under load the spark breaks down. And no amount of cleaning them would fix it. (they looked brand new)
Click to expand...


Good suggestions in this thread but Valvebounce may be onto something here.... likewise, I'd replace cap/rotor/plugwires...a weak spark could certainly be to blame.
 
I have the same carb.. Also check just prior to the needles and seats.. there is a mesh insert up in there that might be plugged?
 
OK, I am going to take this diagnosis a new direction. Try manually shifting into 1st (L1) at a dead stop and launch again. If it is the same feeling then it is not the transmission. Check and make sure the new ignition box has the cover properly grounded. If it is a painted box going on a painted inner fender, I doubt it is properly grounded. Did the car originally had electronic ignition from the factory or was it converted? Get a probe and measure the actual voltage going to the electonic box. If you have 13+ volts you should be fine. If you are finding more like 10-11, someone spliced in the power after the ballast resistor.
 
Gas sat for a solid 24 hours before the jar got grabbed and dumped into a buddy's car, along with the gas pumped out from idling on the bowl =/... Looked and smelled pretty pure to me, and his car hasn't slapped him in the face yet, so I think we can rule out bad gas.

Got about 1/3 of a gallon idling with the fuel line disconnected from the carb, so can I assume it would probably be worth grabbing a fuel pump? If I'm on the wrong track here, let me know!

I'll pull apart the carb when I get a chance, and take a look at things. I tried the launching in 1st idea in January, definitely not a transmission deal. Shifting into 2nd out of 3rd brings rpms up, too, but you still get no acceleration.

Definitely not exhaust, even if the mufflers had plugged, I also tried running it with my cutouts off, basically straight headers, still no change, except in sound level.

sledger46 said:
Did the car originally had electronic ignition from the factory or was it converted?
Click to expand...

The car was, long ago, originally a /6, and I'm not sure if this 318 was the first motor swap or not, but the harnesses all appear correct, and it had been running quite nicely nearly every day for well over a year, when this oddball problem showed up. The block is an early 80's casting number, I believe the rotating assembly is basically stock with KB 167's, the heads are 360's, machined down, the cam is a Mopar Purple 360, the ignition is now a Mopar Chrome box (was a basic stock replacement), MSD Blaster 2 coil, the appropriate ballast, MSD wires, new plugs, and a stock replacement distributor, which I didn't get a replacement for. Yet.

I'm planning on picking up an '85 360 this weekend, and probably keeping the 318 as a backup, so this fix really isn't pressing, but I'll still be waiting on an oil pan and flexplate for the 360, so I'm still working on the fix for the 318.

65Vart said:
I have a 318, does that mean I'm retarded?
Click to expand...

I wouldn't say that... I mean, I'm clearly insane, but I wouldn't call you retarded!
 
And when I say it retards, that's just because that's what it feels like - Kind of like dealing with a computer controlled car, and your fuel curve is messed up because the guy playing with the tune missed something. It's like hitting a rev limiter, except that the limiter is 4500 rpm higher or, in this case, there's no limiter to hit!
 
After pulling the heads back off the 'teen for the 360, I discovered an oddity. #1 cylinder has, quite obviously, not been fired since the heads went back on. Cylinder head is still clean, as is the plug. I will, of course, not be reusing the distributor cap or plug wires on the new 360...
 

Attachments

  • 602908_4523841743861_2003149923_n.jpg
    58.9 KB · Views: 130
Here's my theory:

I think you have dirt in the main jets. The reason it does better when you step on it is that the accelerator pump is squirting in extra fuel which is compensating for the lean condition.

Take the top of the carb off and I bet you're going to find dirt in the bottom of the fuel bowl(s).
 
You must log in or register to reply here.
-

Back
Top