NO ENGINE POWER BACKFIRING

[051743GPW]

Hi

I just finished a ground up restoration of a 1943 GPW, and won a 1st place at a car show last weekend. I thought I would start with the good news, it starts good and idles good and I can increase the rpm with no load and it is smooth and will rev nicely. Once in a while I get a backfire when starting. But when I attempt to drive, it has NO power and basically I must drive in first and really ride the clutch to get going.

I rebuild the carburetor with a kit Ron had, and did not have a metering rod tool so I just set the little metering rod hex nut in the middle of the adjustment on the pump arm. I also rebuilt the fuel pump and the distributor. It has a new coil. I used the static method of setting the timing. It does not appear to have any positive effect when I advance or retard the timing. It might run a very little better with the choke on a little, but not enough to matter. I rebuilt the firewall fuel filter using the original element after I cleaned it. There are no obvious vacuum leaks. I can blow through the PVC valve in both directions? My carburetor rebuild kit had the base gasket with the metal V extending down into the intake manifold? To my eye, it has good spark. It has a new tank, with some paint over spray in it (I was hoping my fuel filter would remove it if any got in the gas). I have rebuilt everything so it is hard to think where to start? Somehow I think it is vacuum leak or lack of gas.

I have a 170 thermostat in it, and it is running at 190? So I think it is running a little hot, does not smell like unburnt gas from the exhaust.

TO SAVE EVERYONE FROM READING THE ENTIRE POST:
I ended up replacing the coil and distributor cap and adjusted the timing. I believe it was more timing than anything.

Mark

[Ben Dover]

Timing could be an issue, first step would be to check that spark plug wires are in correct order after determining TDC. Next would be to use a timing light, it is difficult but can be done., if Timing does not improve the situation, remove the distributor and check the slot in the pump at TDC. Let us know how you are making out if it does not remedy the issue.

[gearhead]

Also take a look at the running engine at night.
Those cool plug rain caps have lots of carbon black and can arc to ground, mine did so i took them off.

Ed

[echelon1]

Sounds like an ignition issue to me to me.
I would start with a new condenser and check if the spark plugs are the right type.

Gindi.

[Ben Dover]

The condenser is an excellent suggestion, could save a lot of work.
The outstanding detail in that restoration is a good indication that whatever is wrong has got to be something simple.

[Stir-Stick]

Howdy,
Check all the above mentioned , and take a closer look at the distributor . Sounds like a timing issue to me (long distance guess ). Check all the screws and springs and weights . Keep us informed and good luck.
Stick

[bazza46]

You say it has no power. Does it still run smoothly, with no power, or does it misfire,running roughly, causing lack of power? if it misfires,check the ignition, especially the condenser, as Gindhi has suggested. I had a jeep do the same, and it turned out to be the new condenser breaking down.

[051743GPW]

bazza46

It starts and idles smoothly and I can increase the rpm's considerably and it is very smooth. Then when I place it in gear and attempt to pull away it will backfire and stammer and miss and if I release the clutch it will stall. But if I ride the clutch considerably I can get it going in first, but second will not happen unless it is flat or down hill and it cannot make a hill in anything but first in low range. Any need for torque will start the backfiring and missing. It will only run in second on the flat or down hill. But it idles very well and increasing the rpm with no load sounds normal. One think I can say is I did touch one of those black boots when it was running and I got a shock.

Thanks for all the help to all. I did not get a chance to look at it today, as things go my tractor blew the hydraulic pump and I spent the day with that.

Mark

[bazza46]

Seems exactly like the symptoms of my jeep with the (new) faulty condenser. Try another one. They're easy to fit. While you're at it. check the points gap. A very large gap will reduce dwell time so coil can't produce sparks at speed or under load.

[F. R. Fox]

I rebuild the carburetor with a kit Ron had, and did not have a metering rod tool so I just set the little metering rod hex nut in the middle of the adjustment on the pump arm

Did you remember to put that dinky little spring back on the pump arm?

[Ben Dover]

Are the spark Plug Wires Copper Core?

[echelon1]

There are faulty spark plug rain caps on the marked.
It is funny to see how these "rubber" caps are sparking with the head.
Try the jeep with the rain caps removed and the issue might dissapear...

Gindi

[051743GPW]

Joel, yes the wires are copper core!

F.R.Fox, attached picture of the pump arm and metering rod.

Thanks again for helping me.

Mark

[echelon1]

Mark, The rubber caps on the spark plugs (rain caps) can be your issue.
Some have found to spark with the head.

Gindi.

[051743GPW]

Gindi, I will remove the rubber boots today and check. I know I touched a boot when it was running and I got shocked.

Mark