carrier carb question

[Jim Burrill]

My really bad weekend as a mechanic..... (sigh)

mk2 carrier cranks but won't start unless I giv eit a shot of either. Choke in various positions gs to the carb, etc.
Once it catches, the engine runs strong and sounds good. Just getting it started.

Is there a specific part of the carb to check for the hard starting issue?

Thanks in advance.

Jim

[Jordan Baker]

It's possibly electrical. Are you running a stock distributor? When cranking, the starter might be taking too much power away from the distributor. With the ether having a lower flash point, what ever spark is present might be enough but not enough for gasoline.

[rob love]

Another possibility is the fuel pump check valves are cracked. At low cranking speed it is not enough to overcome the slight loss from the cracked check valves whereas at running speed it's OK. If you pull the lines into and out of the pump, and hook up a line to the outlet, try blowing backwards through the pump. If you get any air loss through the pump, then either the diaphragm is torn or the check valves are leaking.

Personally, I stay away from the ethanol fuels on both my own vintage vehicles as well as the museums, and that has helped a lot.

But the voltage one is also a possibility. On my carrier, I have a 12 volt battery which is dedicated strictly for the starter, the remainder of the vehicle is on the 6 volt system. Since there is no draw against the 6 volt system on start up, everything works vetter than original.

[Jordan Baker]

Rob, good points about checking the fuel pump and lines. However I don't think it would be the issue in this case. Would not a change in choke position account for a lack of fuel in start up with helping to make the fuel richer and therefore start?

[rob love]

No. Whatever is in the carb will often disappear on these older engines with the after boil. With bad fuel pump checkvalves, everything in the lines and pumps goes downhill back to the tank, or some of the fuel in the lines will also afterboil.

If there is a slightly leaking checkvalve (just one) the pumping performance will go to crap. Cranking speed just won't do it. Running speed will/may.

I picked up a dozen M38A1 pump kits a lot of years ago, and cannot count the different pumps that I have used those valves in. Just in the last 6 months I fixed a Jeep pump (uses 6 of the checkvalves), a pump in the museums white scout car (uses only two of the checkvlaves), and a carrier engine.

[Jordan Baker]

Good to know. Thanks.