251 motor will not fire up again? HELP!!!!

[Geekay]

I have had the 1954 Dodge Suburban ambulance for a short while, 251 motor that had done little work. When it arrived after a 6 hour trip on a car transporter it would not start (cranking but not firing). We eventually found that the clamp on the distributor had warped and was enabling the distributor to twist when we cranked it, thus mucking up the timing.

With that sorted, it started eventually. We did have a massive backfire which blew apart the muffler, caused mainly because of the fuel build when we kept cranking it.

An electric fuel is fitted without a separate switch, so when ignition was on, and we were cranking it, it keeps fuel pressure up. I have since fitted a separate switch so I can turn the fuel pump off in need.

With a timing light I set number one at TDC and it idled and ran quite well (stationary) for a few weeks. Great.

Next job was to install new brake master cylinder, fluid, bleed these. Now I have brakes. Even better, I can drive the Dodge around the yard a bit. Our block slopes a bit so I was reluctant to drive it just relying on emergency brake to stop.

So, give it a small drive, engine goes okay, but lacks a bit or power. Probably just need to revisit timing with vacuum disconnected and do the timing properly. Easy. Starts easily a few times that week.

The next week I went to start it again this and engine is just barely running, small coughs and little backfires. Damn..looks like timing is out again.

After hours of trying to "fix" this, it is back to cranking, not firing.

No matter what I do I cannot get any firing at any cylinder and I have exhausted my knowldege/ability, so next step is to get it to a mechanic and pay them, unless someone here can help.

Here is a potted history of events:

At one point the carby (Stromberg) float ceased working and fuel poured out of it everywhere. Took it apart and the clip on the float had dislodged and float was not working. Took the opportunity to clean the carby again, replaced pin on float, re assembled carby and installed it. Have not connected the Choke cable. Checked fule flow from electric pump at the carby and it is good. Fuel is fresh and has half a tank.

Carby appears to be functioning. When I press the throttle linkage there is a good spray of fuel evident. Trying to eliminate fuel as the issue I have even poured a small amount of fuel down the carby and also tried Aerostart, but neither will get a piston firing.

So, must be a spark issue, surely?????

I have taken the distributor out, checked all wirings and they are sound. Points set with dissy on the bench, gap 15 thou.

With crank handle turned motor to get number 1 at TDC, and rotor cap is at 7.00 o'clock book.

I bought a plug test light that goes between the plug and the ingition lead to see if there is power to the plug. Yes, number  1 has voltage at TDC, and dissy rotor at 7.00 oclock. All other leads have voltage too. Cleaned and reset plugs.

Took the coil to auto electrician and he said it is good and strong. Changed condensor at one stage too but no difference.

Brand new big battery so plenty of power available for strong spark.

One weird thing is that even though my lead test light will flash to show voltage to the plugs I now cannot get the timing light to "flash". Even bought another one and same..no strobing". Tried using a battery back up pack to power the timing lights rather than the Dodge battery, but still neither light will strobe on any plug lead. Made sure the plug lead was not tangled with another lead in case that upset the signal. Both timing lights have these new clips that go over the plug leads, with an arrow that needs to pint towards the plug.  Maybe I need to get a steel spring attachment that goes between the dissy number 1 outlet and the start of plug lead and put the clip over that? The plugs leads are nearly new. Dissy cap seems to be in good order.

HELP!!!!

 

 

 

 

 

 

 

[Don Coatney]

Sounds as if you have flooded the engine several times in your attempts to start it. Have you replaced or at least cleaned the spark plugs between each flooding incident?

[55 Fargo]

Well you have fuel to the carb, and you tried to prime the carb, are the spark plugs wet with petrol after cranking?

Pull some plug wires, and check to see you are getting a nice blue spark when it is very near the engine block.

So you need 3 things,

1) fuel delivery, carb is spraying fuel

2) you have fire (spark), from power to the colil, coil to the distributor cap, through the breaker points, down the high tension wires to the sparkplugs.

3) you need compression, have you done a compression test?

These engines will run if timing is off, a bit, fuel+spark+compression=fire

[PT81Jan]

15 hours ago, Geekay said:

...

One weird thing is that even though my lead test light will flash to show voltage to the plugs I now cannot get the timing light to "flash". Even bought another one and same..no strobing". Tried using a battery back up pack to power the timing lights rather than the Dodge battery, but still neither light will strobe on any plug lead. Made sure the plug lead was not tangled with another lead in case that upset the signal. Both timing lights have these new clips that go over the plug leads, with an arrow that needs to pint towards the plug.

...

Hey Geekay,

sounds like an similar issue that I had two weeks ago. At first only a little bit lack of power. Some days later slightly stuttering when accelerating, slowly getting worse …

The timing was not perfect but not bad. Slightly adjusted it according to spec., test light worked.

But after that I also had no flashing test light when it should. Took also another one …

I noticed then that the breaker certainly did move, but didn`t really break when the distributor cam was in the firing position. Lifted it with the finger nail and had a flashing test light …
At the end it was a simple problem: The breaker was not set correctly. I think it had a minimum clearance before I corrected the timing and thus had a weak spark with the effect described above. After correcting the timing, the breaker had no clearance and thus no flashing test light and thus no spark.

Properly adjusted, everthing works well !

Good luck, Jan

[Geekay]

Thanks everyone.

Jan, I will check the breaker again, and see if I can get a nice blue spark at the plug as per 55 Fargo.

 

[Dave72dt]

Check for a spark at the points when turning it over first.  You need to have that before you'll get any at the coil or plugs..

[bambamshere]

Just wondering your points are set a .015 are they not supposed to be set at .020. I have a 56 Fargo with a 251 in it that is set at that runs good. Spark plugs are set at .035. Just a suggestion.

[Fernando Mendes]

I will check first all the primary circuit if it is not shorting with an ohmmeter.If the primary circuit is shorting,the current will not arrive in the breaker arm.Please check it first.

[countrytravler]

Update

[Geekay]

I have decided to buy new coil, points and condensor.

Dissy (Lucas) number is  DM6A 40388D

I have searched on line however unable to find where to buy these.

Anyone help.

[NiftyFifty]

Possibly time to switch from Lucas? Lots of Autolite or even move to the newer electronic dizzy and new coil