Engine problem

[nelle]

I am having a strange problem with 230 flathead in my 47 WD-20. After have driven about 1 or 2 miles from the house, engine starts jerking in a regular rhythm of about 2 jerks (misses) per second when going about 35 or 40. Strangely, it does not do this consistently. Some days it has run just fine for 5 or 10 mile trips.  Here is what I have done so far to try to alleviate the problem:  check for debris in gas tank (none); drained and examined fuel in tank (clean) put on spare carb I had; put on different coil; replace plugs; replace points / condenser.  Still starts the jerky rough running after 1 or 2 miles.  It has me perplexed.  I'm not a good mechanic like a lot of you guys but would like to figure this out. Distributor has mechanical advance.  Perhaps will try new plug wires next.  Any help or ideas appreciated.

Steve

[JBNeal]

Ya might want to examine that ground wire from the coil to the distributor...does the problem occur only when the truck is moving, or can ya reproduce it after it occurs when the truck is parked?

[nelle]

Thanks JB. Will try that.  I cannot reproduce the miss when the truck is idling.  Only when going 35 or 40 after it gets fully warmed up.  

[Jeff Balazs]

To me this kinda sounds like a fuel delivery issue. Could be the fuel pump or a partially collapsed fuel line.

Hth, Jeff

[kencombs]

9 hours ago, JBNeal said:

Ya might want to examine that ground wire from the coil to the distributor...does the problem occur only when the truck is moving, or can ya reproduce it after it occurs when the truck is parked?

Good idea!  especially close attention to the wire from the distributor's outside stud to the breaker plate. 

[nelle]

Jeff - thank you for that suggestion.  I had previously rebuilt the fuel pump and it has run good after that.  As far as fuel line collapse, there are only two short segments of rubber line and those appear to be in good shape, not flimsy or thin. Steel line is sound, no kinks.

 

Why would this miss be so regular (two jerks per second) while going 40 mph, but then go away as you ease off the gas - but this is only after driving 2 miles or so.  Seems strange to me.

[Blue]

Did you check the springs on the mechanical advance while you were in the distributor? It's a stretch, but something to think about. Does it run fine at 40 until it gets warm?

[nelle]

Thank you for the suggestions regarding wire from coil to distributor and then inside to breaker unit.  All appears sound and same problem persists.

Plug wires look good externally but I wonder if they can be cross firing since some of the wires are longer than they need to be and cross each other.

[nelle]

Springs on mechanical advance - not I have not checked them, nor have I even opened that compartment up.  Yes it seems to run fine at 40 until I have driven about 2 miles, then the problem begins abruptly.  Slow down and I can make it home @ 30 mph.

[Blue]

Fuel delivery makes a lot of sense, but it seems you have checked everything. I had an old Jeep truck with a similar problem and it was a pinched fuel line. How are your temperature and oil pressure gauges when the jerking is happening?

[Plymouthy Adams]

 again, this is an all to familiar report from the members here after a tune up.....the new points have springs that must be put in place to be effective....seems they are no longer assembled as part of the breaker points but inserted on installation......many members tend to think this is an optional spring...it is not optional....just an added step in the points installation...test for point float....17 to 20 ounces of spring tension is required...to move the floating contact breaker arm...may not be your problem..but still would be an item to ensure is right when you truly may not know what is wrong....

[Blue]

1 minute ago, Plymouthy Adams said:

 again, this is an all to familiar report from the members here after a tune up.....the new points have springs that must be put in place to be effective....seems they are no longer assembled as part of the breaker points but inserted on installation......many members tend to think this is an optional spring...it is not optional....just an added step in the points installation...test for point float....17 to 20 ounces of spring tension is required...to move the floating contact breaker arm...may not be your problem..but still would be an item to ensure is right when you truly may not know what is wrong....

You certainly could be right, but he is saying he performed a tune up because of the problem.

[nelle]

Oil pressure is 40+ and water temp is something like 150 when this happens. the engine runs cool, probably too cool and I know I need to check the thermostat to see if it is stuck open.  These are both after market gauges.  I would love to get original oil and temp gauges into this truck.  I suppose there are a hundred guys who want the same thing - hard to find.

[nelle]

Yes regarding spring on points, it was a bit tricky getting the spring and the copper element in the right position (did all of this with dist installed).  I can try to check spring tension but it seems pretty tight to my "finger gauge".  In fact the first set  Blue Streak I bought only lasted a few miles before one of the contact tabs broke off and left me stranded.  I suppose the quality of these parts is not as good as we remember from the old days. Second set has held up.  

[Young Ed]

1 hour ago, nelle said:

Oil pressure is 40+ and water temp is something like 150 when this happens. the engine runs cool, probably too cool and I know I need to check the thermostat to see if it is stuck open.  These are both after market gauges.  I would love to get original oil and temp gauges into this truck.  I suppose there are a hundred guys who want the same thing - hard to find.

OEM oil gauge should be easy. If you had a W series I've got a box full of them. The OEM temp gauge is harder as the tube breaks fairly easily but they can be repaired

[Plymouthy Adams]

8 hours ago, BlueberryDodge said:

You certainly could be right, but he is saying he performed a tune up because of the problem.

yes....a good effective set of points after a lot of use will decay right to the point of uselessness and cause a lot of problems, hard starts, failing under load.  Switching out these to new and overlooking spring tension will get you back to possibly easier start, nice idle and low end and fall on its face at higher speeds.  This is the reason I made the comment, just because it is new, does not necessarily mean it is right...again...when  you do not know what is wrong, prove what is right before you move forward overlooking a simple problem.

[David A.]

I had a problem with my 38 Buick. It would run fine around the yard and short slow  trips, but if I tried going more then 5 miles  or running at higher speeds, it would die. Someone on another truck thread was having a similar problem and was told the reproduction gas caps were not vented. Longer trips and faster speeds caused a vacuum in the gas tank and was starving the engine. I checked my Buick gas cap and sure enough, no vent hole. I haven’t had nice enough weather to try it with a vented cap, but I’m hoping that will solve my problem. Might be worth checking as it seems you have checked everything else. 

[nelle]

Thank you for that suggestion.  This is the original gas cap and the air vent is present and not plugged.  I did have that same problem on my 1950 B2B which I sold last year.

[Jeff Balazs]

I still think it is a fuel delivery issue. Try pulling the carb off and give it a close inspection. Perhaps some dirt lodged somewhere? or an orifice plugged up. I have to say that you almost can't filter the gas enough these days. I have also found that with the ethanhol in these modern fuels regular use of a fuel additive like MMO is helpful.

Hth, Jeff

[JBNeal]

To clarify:  you can estimate engine rpm by sound and by calculating using indicated speed, tire diameter,  axle ratio, etc.  When the problem occurs while in motion, estimate engine rpm, then try to duplicate the problem with the truck parked but increasing engine rpm.  If the problem cannot be duplicated while parked, then the problem has a vibration or momentum component...

 

I always fall back on checking ground continuity on these old buggies, as they are prone to electrical issues when corrosion is present at every path to ground.  One way to verify continuity is to run temporary jumper wires that parallel a circuit...this is one way I found that my ignition coil on my '48 had a weak ground path, as a jumper from the coil ground to battery ground really woke that engine up during testing...I replaced the defective wires, cleaned mechanical attachment surfaces and lubricated threads with electrical contact grease to displace moisture, and the engine had more noticeable power climbing hills...

 

Your issue sounds like some kind of dithering, which could be indicative of a weak ground path or insufficient fuel delivery...I would not rule out a fuel issue just yet, but my experience is that fuel issues have a surge effect, as fuel pressure gradually falls off until ignition terminates, but engine momentum allows mechanical fuel pumps to continue to build pressure, so ignition may start up again as long as the engine continues to spin and spark delivery continues.  Electrical issues have a more rapid effect, either complete ignition shutdown or rapid interruption of signal.  Dithering in these low voltage system can best be determined with analog multi-meters as they can show real-time results with needle bouncing, whereas digital multi-meters tend to have slow, intermittent results that can hide the peaks and valleys of current delivery.

 

If the engine problem can be duplicated with the truck parked and engine rpm increased, then the analog multi-meter will be needed to check voltages at increased engine speeds...this will greatly aid in zeroing in on any electrical issues

[Veemoney]

I had issues in the past similar to yours (truck jerking and having to reduce speed to get it to stop jerking on my 47 WC. It was fine idling and taking off from the light but would start the jerking in 4th. 

 

I am thinking fuel starved after warmed up. I say this because you have not mentioned any backfiring at all. I would expect some misfire if the ignition was at fault while you were running. The fuel pumps pump at low pressure and it doesn't take much to restrict them. Below are my thoughts in the order I would check them for the fuel system

• If you have a fuel filter inline confirm you can easily blow through it manually. I could see gas in mine while running in the driveway but when I removed it and blew into it I could feel it was restricted and replacing it resolved my issues.
• I see you rebuilt your fuel pump but the issue could still be there. My truck is running a 6volt fuel pump now  but 12v are also pretty inexpensive. you can bypass your pump and see if that resolves your issue.  
• Did you check the float adjustment in either of the carbs or the needle valves. You did not mention if these were rebuilt or checked so if not confirm this. 

Good luck

[nelle]

Jeff - thank you for the reply regarding carb and fuel delivery.  I did not rebuild or even clean the carb that is on there now.  However, this funny problem is happening exactly the same for both the old carb and this one.  The first was a Stromburg and the current one is a Carter Ball and Ball.  Since they do the same thing I can't imagine that it is a carb issue.  However I know I should clean and rebuild.I know I will get scolded on this but the only filter in the system is the glass settling bowl and fine screen at the mechanical fuel pump.  I need to add a filter.  However, since this problem does not happen until 2 miles from the house, it seems there must be another issue besides lack of filter.  But I am going to do as you suggest. 

[nelle]

Thank you Mr Neal.  I cannot duplicate the problem in the driveway.  I have tried. Runs fine in driveway even at approx engine speed when the problem occurs.  Must be a difference when under load vs no load. It puzzles me why the issue only happens after driving 2 miles.  No problem at all getting to the 2 mile point running at 40 and with several starts and stops.

[Big Red Rustmobile]

I had a problem near identical to your description with the B1D years ago. It turned out to be the distributor bearing. I sent the distributor to a place in Pennsylvania for a rebuild (I don't remember where ...this was back in the 90's). When I put the freshly rebuilt distributor back in, the problem was gone. The rebuilder described the problem as a "crystallized bearing". I'd never heard of bearings crystallizing before then, but apparently it has something to do with them aging. Hope this helps.

Edited January 20, 2019 by Big Red Rustmobile
ambiguous description of what 'it' is in the second sentence, referring to distributor

[Plymouthy Adams]

do not rule out the possibility of a coil heat issue....gets hot, degrades, loses power.....I would have to ask if when this happens, does the vehicle when shut off start immediately with no apparent issues...if you have a hard start and later it will start....coil is often a go to...you can physically cool the coil also as a weed out test.  does not cost but a minute of your time and a bit of ice packed about the coil to sink the heat.