Difficulty with cold start

[Crusader_22]

Hi,

I just recently got my M151A2, and have been having a lot of trouble with getting it started cold (after sitting a day).

The truck has a '77 engine, full sealed fuel system, Zenith carb, and is all there and military 100%.

My start procedure is full choke, no throttle (or pumping), and I get an occasional sput....sput.... Then, eventually, a series in enough of a succession to add up to it starting, or not. Once I get it running (which I currently cannot), and warm it to op temp, it starts instantly and easily.

I checked for vaccuum leaks while running with the starting fluid, spraying it on the intake system, and no RPM increases, so I think I am good there.

I have cleaned and gapped the plugs, tried priming the fuel system (that worked the first time I started it when I got it home), and varying choke position, throttle, etc. Nothing seems to make much difference, it just randomly chugs until it starts sometimes. I even tried starting fluid, but that really made no difference. I don't like that stuff anyway.

My next plan is new plugs, then a new electronic ignition unit, and investigate the fuel pump to make sure it is good. It does pump fuel, though, I cranked it with the line off and it squirts out.

Any other suggestions? It's pretty frustrating. Even though I don't have plates for it yet, so all I do is start it and stare at it, or occasionally buzz up and down the alley!

Jeff

[67mutt]

Try ignition timing. Mine is very finiky about the timing. If its to far retarded, it's difficult to start, and tends to load up when idling for longer than 3-4 minutes. If its to far advanced, it will try to kick the engine backwards when starting, and its hard on valves also. Mine seems to like about 12 deg B.T.D.C. with currently available gas. A timing adapter wire can be made from an old plug wire with the shielding stripped away. A conventional inductive timing lite can then be used. Just connect the battery leads to ONE of the batteries (not across both, as a conventional lite is 12v.only, and across both batteries will give 24v.) and the other lead to the unshielded wire. The adapter wire should be installed in place of the #1 plug wire for the test. Factory advance is 6 deg. Line up the line on the pulley with the pointer wire on the timing case and you have 6 deg. The rest is kind of trial and error. Hope this helps.
Bob

[Crusader_22]

Thanks, very much, I will try that. I will have to figure out something for a plug wire, I have no spares. The loading up after idling is also something I am experiencing.

Which way do you rotate the distributor for advance?

Jeff

[Fil Bonica]

Remember the old addage Fire or fuel..
I would look at the distributor and confirm 24 volts at the input and at the coil There is an inline filter capacitor that has been known to go bad You can jump it out if necessary to test . Check the cap, rotor and see if you get a good spark off of each wire as someone turns over the engine.
You could find a lot of things just doing these tests.
Intermittant power, bad filter cap, bad coil bad or carboned cap or rotor or bad electronic module.
Timing usually isnt that far off unless someone really screwed with before.

I am sure somebody else will chime in with other helpful suggestion. In the mean time this shoud keep you busy.

By the way where are you located?

Fil Bonica

[Crusader_22]

Thanks, Fil. I'll check that, too.

I'm in Tucson, AZ.

Jeff

[rickf]

Timing should be 6 degrees and if it is of by more than a couple of degrees you will most likely have driveability issues. 6 degrees is when the marker is right on the line. It sounds like the carb needs a good cleaning but definitely follow what fil said also. It sounds like you folowed my "things to try before asking" post.


Rick

[raymond]

You can time the vehicle by getting a piece of wire core spark plug wire and cutting it off and sticking one end in the distributor cap and the other in the end of the spark plug. It will spark sufficiently for timing the vehicle.

[67mutt]

To advance your timing, turn the distributor clockwise I THINK!!! Its been several months since I've messed with it. As a general rule, as you advance, the engine idle will pick up some, as you retard it, idle will decrease some. There are no markings other than 6 deg. so go in small increments,and road test with engine at operating temp. If you live in an area with real gas, 6 deg. will probably be OK. I live in southwest Ohio, and the E.P.A. likes to tamper with our gas formulations, and it seems to throw things out of whack for me, so I have to do some extra tinkering.
Bob

[Crusader_22]

Thanks, guys.

It turns out I had a good moment - I forgot I had an inline (not inductive) timing light, great for putting it inline between the wire and plug. Then I realized the strobe is shot.

I did sort of randomly move the dist. in small increments (after marking the original position) to try for the "hunt and peck" method, but to no avail.

Going back to the list, "make sure batteries are fully charged" LOL.

Everything else on the "check this first" list is covered except carb disassembly and cleaning, but my friend (previous owner) did that with no positive result.) I am suspecting ignition at this point, and possibly a tired fuel pump (mechanical).

Jeff

[Crusader_22]

Progress report...

Got it running. Recleaned and regapped the plugs (AGAIN) at .030, I had them at .035. They were filthy. They need to be replaced.

Moved the timing slightly, runs and idles better now. Still a stumble at accelleration sometimes.

Sure likes the choke, as per the reading I have done!

Thanks, guys.

[Crusader_22]

AMAZINGLY, my local NAPA auto actually had two Autolite 2245 plugs in stock! I just put them in, it starts and runs better than ever. (the #4 and #3 plugs were the best of the old ones, so the new went into 1 and 2). Amazing difference. Started right up and ran like a champ.

Now, I just have to see how it goes after sitting overnight.

So, in summarry for the sake of posterity and future searches,

- I cleaned the rotor and cap contacts
- reset the timing (sort of...added a little advance)
- cleaned the inline fuel filter
- cleaned two plugs, replaced two (two more on the way)

Still don't know if the fuel pump is losing prime. We will see. Anyone know of a source for a "backup" 24v inline electric fuel pump?

Jeff

[toptiger]

i got mine from
http://www.saturnsurplus.com/m151/m151.htm
fast same day shipment. I spoke with Jay.
I think it is a good idea to get one and have on hand just in case, so I also have a spare.

[Crusader_22]

Final analysis:

Starts instantly every time, 24 hour sit had no effect.

Thanks to all who helped!

Jeff