Engine Dies after Few Minutes in Gear

[edwardc]

My engine was running fine, except for a weeping water leak on the head. This turned out to be from a crack, so I got the head replaced. Now I have a new problem.

Engine starts easy, runs great. Like a sewing machine. Good water flow, good oil pressure. I put it in gear while tied in the slip, and run it up to 2000-2200 rpm ( I have a 2:1 V-drive). After a few minutes, the temp is up to 110 and it starts to sound a little uneven. Then it starts to occasionally miss. This quickly gets erratic and worse until it stalls, sometimes with a backfire. If instead, I throttle back a little, it helps breifly, but still eventually stalls. After it stalls, if I immediately take it out of gear, set to idle, and hit the starter, it starts right back up and runs smooth.

Here's what I've tried so far, with no effect whatsoever:

1) Drained the carb to check for water or dirt. None found.

2) Drained fuel filter to check for water. None found. Replaced Filter.

3) Checked centrifugal advance in distributor. Mechanism is functional. Verified centrifugal advance with timing light.

4) Adjusted idle timing to everywhere from 0 deg to 8 deg advance. No effect on stalling.

5) Replaced coil. No effect.

6) Tried applying choke when missing starts. Had no effect.


At this point, I'm out of ideas. Need help!

Since the engine was running fine before the head replacement, I'm suspicious that this problem is related. Is that even possible? Can a leaky head gasket produce these symptoms?

Help!!

@(^.^)@ Ed
1977 Pearson P-323 "Dolce Vita"

[hanleyclifford]

Try using a different condenser.

[thatch]

Tank pickup problem?

edwardc,
Sometimes when an engine backfires it is running out of fuel. The symptoms are consistant with a blocked fuel tank pickup. If this is the case an engine will normally run for a while and then gradually starve for fuel. An easy way to check this is to blow back through the fuel line as close to the tank as possible and then check to see how long the engine will run. If the run time has increased then debris in the tank is probably the problem.
Tom

[edwardc]

Try using a different condenser.

I've got the Ignitor electronic ignition, with the pertronix distributor, from Moyer.

@(^.^)@ Ed

[edwardc]

edwardc,
Sometimes when an engine backfires it is running out of fuel. The symptoms are consistant with a blocked fuel tank pickup. If this is the case an engine will normally run for a while and then gradually starve for fuel. An easy way to check this is to blow back through the fuel line as close to the tank as possible and then check to see how long the engine will run. If the run time has increased then debris in the tank is probably the problem.
Tom

But if the engine were starved for fuel, is seems I'd have to crank it for a bit until the carb refilled. This is not the case. A quick "blip" on the starter is enough to restart it.

I have a facet electronic fuel pump, and a large Sierra filter. I know from changing it that it takes some time for the pump to refill it and the carb.

Still, the symptoms do sound like a fuel problem. My initial thought, and that of others, was that there was a drop of water in the bottom of the carb bowel, and under the higher fuel demand under load, it would get sucked to the jet and momentarily block the fuel. I pulled the plug on the bottom of the carb and caught the fuel in a container to check it for water, but there was none.

@(^.^)@ Ed

[msmith10]

Agree with Tom. It's a free test. Also check for air leak into fuel line. Do you have a priming bulb? If not, install one. Then you can use this to pressurize fuel system when problem starts, and also check for air leak.
You'll want one anyway with an electric fuel pump so you can easily reprime system after filter change.

[thatch]

Side check

edwardc,
I'm hoping that the problem is fuel related because there are only so many pieces that can be cleaned or replaced before the trouble is found. I hate to head in another direction this early but there is another test you should probably try. After warming up the engine to the point of dying again, remove the lowest spark plug, (in the case of your V-drive version probably #1) and check for water. It is possible that a minor crack in the cooling system, which is widening with rising engine temperatures, is allowing the engine to start and run for a while before causing a cylinder flooding issue. Again, I hate to bring up this possibility but the symptoms are eerilly similar to another A4 owner's recent block problem.
Tom

[tenders]

A couple of thoughts to help figure out whether it's temperature causing the engine to stall, or elapsed fuel, or fuel flow rate. Can you run perpetually at lower speeds? What if you vary speed, say, a minute at low speed and a minute at high speed, and then back to low again. Will the engine run indefinitely? Have you checked the fuel pump for consistent outflow? Perhaps there's some sort of a blockage or degradation in the pump preventing full output.

[RGrenier]

Also make sure the tank vent is not blocked.

[edwardc]

Solved!

I want to thank everyone for all the helpful suggestions. As most of you suspected, it was a fuel restriction problem. But a weird one.

First, I pulled the fuel line off the carb and energized the Facet pump. Decent pressure, but almost no flow. This eliminated the carb as the source of the problem.

Next, as Tom suggested, I pulled the fuel line off of the inlet to the filter and blew back through it to the tank. It was clear and blew easily! This just left the filter and the pump. Since I had just replaced the filter, I now suspected the pump was bad.

I re-plumbed the hoses to hook the pump directly to the proven-clear tank line and led its outlet into a container. Same pitiful flow! Must be a bad pump! I disconnected it and removed it from the boat, expecting to have to buy a replacement.

Out of curiosity, I opened it to inspect it, now that I could turn it upside down and see into the bottom. The filter screen was clean (I had already checked it once before) so I started examining the ball valve in the center. I pressed on the ball with my fingertip, and at first nothing happened. Then, it suddenly went "click" and came free, moving easily now with fingertip pressure. I suspect that the alcohol that's now added to gas had softened the rubber seat under the ball, causing it to stick over the winter. This was the source of my fuel restriction! Apparently, enough gas was getting past it for the engine to run without load, but not much more.

Hopeful now that I didn't need a new pump, I quickly reinstalled it and repeated the last flow test. I was rewarded with a tremendous flow!

Finally, with everything put back together, I was able to run the engine under load at 2400 rpm for a half hour without a problem. Temp came up to 140 and held there rock steady. Success!

In the future. I'll know to press on that ball valve to check it when cleaning the pump's filter screen during spring commissioning. Has anyone else seen this kind problem in the Facet pumps before?

[Marian Claire]

Thanks for the follow up. Good info for those with the Facet pumps. Dan S/V Marian Claire

[thatch]

Victory!

edwardc,
Thank's for allowing us to ride along on your troubleshooting journey. Each time we do, we gain a little more info about our engines and it's systems. In this case, which may or may not have been the actual cause for the fuel pump check valve sticking, is that we need to be reminded occasionally that there is now alcohol in our fuel and that it can cause damage to older rubber or plastic parts.
Congrats again, Tom

[edwardc]

edwardc,
Thank's for allowing us to ride along on your troubleshooting journey. Each time we do, we gain a little more info about our engines and it's systems. In this case, which may or may not have been the actual cause for the fuel pump check valve sticking, is that we need to be reminded occasionally that there is now alcohol in our fuel and that it can cause damage to older rubber or plastic parts.
Congrats again, Tom

Thanks, Tom. Always glad to share.

A further note. I have the recommended Facet pump model 477-060E, not one of the earlier trouble-prone models. The specs claim it's rated for diesel, gas, gasahol, or pure alochol. But SOMETHING made my check-valve stick!

[Baltimore Sailor]

Thanks, Tom. Always glad to share.

A further note. I have the recommended Facet pump model 477-060E, not one of the earlier trouble-prone models. The specs claim it's rated for diesel, gas, gasahol, or pure alochol. But SOMETHING made my check-valve stick!

Just another visit from our old friend Murphy.

[mgraham49]

When you replaced the ignition, did you replace the coil? I have the same problem, but did not replace the coil. I have not yet rebuilt my mechanical fuel pump, since it is putting out some. But because my engine starts immediately and then limps before it dies for a few seconds, I had thought coil instead of fuel. Does an engine with a bad coil, limp, or just not work at all.

Mike Graham, Bali Hai.