Low Manifold Vacuum

[dozer_xj]

Bought this 54 m37 NOT RUNNING Last fall. "Ran when parked" 10 years ago. I have fresh fuel to the carb, new plugs, electronic ignition, adjusted valves (They were tight) replaced broken exhaust manifold so intake and exhaust gaskets are new, rebuilt the carb. Tried firing it up and it only sputters. Put some oil in the spark plug holes to help the rings. Nothing. No sputtering. Tested manifold vacuum and with the choke on it only pulls 2" of vacuum. Junk motor? Leaky PVC valve? HELP! OUT OF MONEY AND PATIENCE!

[just me]

What is compression?

[isaac_alaska]

it will run with no PCV valve. i ran mine for a while with a rag stuffed in the hole, and it was happy. compression test would be a good idea. if that passes, then you need to look at the timing. as well as make sure you got the plug wires back in the correct order. did you verify you have spark? easy to check by yourself, you can reach the starter lever from teh drivers fender and see a plug, just be sure to stay clear of the fan.

[dozer_xj]

I have a nice bright blue spark. I I left the plug wires on the cap and put the ignition module in with the distributor still in the truck. Someone on a facebook group mentioned after they converted theirs that they had to change timing to even get it to run.

Went out this morning before work to try it one more time. It almost started. It spit and sputtered and the vacuum went up to 10 inches. I did not have the temporary electric fuel pump going. It may have started if it did. Going to try turning on the fuel pump tonight and if that does not work I will do a compression test .

[RMS]

I have a nice bright blue spark

there's your problem it should be red to orange
2lbs of vacuum @ cranking speed with a 24v starter on 24v is normal. if your cranking with the choke all the way out pulling 2lbs you will flood the manifold in seconds if the (vacuum operated) throttle pump is working correctly. crack a fitting on the lowest point of the pvc (Douglas valve) piping and I bet you gas will leak out after cranking for a few seconds. pull the plug on the back of the manifold and use a strip of paper to see how much gas is pooled in the manifold. my 52 likes to start with 3 clicks on on the hand throttle and a quick blip of the choke (in and out quickly) any more choke than just a blip and she floods.
the dark green Canadian wants 4 clicks and half choke when cranking.

Put some oil in the spark plug holes

that will only get oil on the valves.....well unless their closed.

an easy way to check timing is to spin the motor by hand till your on the compression stroke on no1 set the crank between 2 and 4 before top. verify the rotor is pointing to no 1,reinstall cap, ignition on, set screw loos, no1 lead almost grounded to block or with spark plug sitting on head, twist dizzy till it sparks then tighten set screw.

[dozer_xj]

I have a nice bright blue spark

there's your problem it should be red to orange
2lbs of vacuum @ cranking speed with a 24v starter on 24v is normal. if your cranking with the choke all the way out pulling 2lbs you will flood the manifold in seconds if the (vacuum operated) throttle pump is working correctly. crack a fitting on the lowest point of the pvc (Douglas valve) piping and I bet you gas will leak out after cranking for a few seconds. pull the plug on the back of the manifold and use a strip of paper to see how much gas is pooled in the manifold. my 52 likes to start with 3 clicks on on the hand throttle and a quick blip of the choke (in and out quickly) any more choke than just a blip and she floods.
the dark green Canadian wants 4 clicks and half choke when cranking.

Put some oil in the spark plug holes

that will only get oil on the valves.....well unless their closed.

an easy way to check timing is to spin the motor by hand till your on the compression stroke on no1 set the crank between 2 and 4 before top. verify the rotor is pointing to no 1,reinstall cap, ignition on, set screw loos, no1 lead almost grounded to block or with spark plug sitting on head, twist dizzy till it sparks then tighten set screw.

This is good info. I will give it a try tonight!

[dozer_xj]

Broke lose the pcv valve fitting and fuel poured out. Turned it over and there was a ton of suction on the crank case side of the pcv valve. I wrapped electrical tape around it and my cranking vacuum went up to 5 inches then it went to zero and there was fuel running out of the tape I put on the pcv fitting

Anyone know what the bench setting on the idle fuel adjustment on the carb is?

[RMS]

4-7psi on the fuel pump. with the top of the carb off, set the float just above the bottom of the cutout in the throttle pump bore. turn on electric pump or hand prime the stock pump to insure proper operation of the check. reinstall top cap. turn the idle screw all the way out and use the hand throttle notches. the mixture screw is about 2 1/2 turns out pointing usually @ 1 O'clock for lean and 11 O'clock for rich @ sea level. be gentle screwing it in. and don't forget kids if the throttle linkage fails the carb goes to WOT

[52PLOWERWAGON]

try pull starting it in 3rd gear low range

that's the only way mine will start

[dozer_xj]

try pull starting it in 3rd gear low range

that's the only way mine will start

I might just have to give that a try. Worst case it will give me the sensation of driving it!

[RMS]

wouldn't it be best to get everything set up right first ?

[dozer_xj]

OK so with the PVC valve undone, I turned the electric fuel pump on for about 90 seconds and it DID NOT leak and fuel. That makes me think the float is doing its job but when I crank I get a fuel drip.

[dozer_xj]

Since I did the compression test I have had the plugs out of the motor. I ran the electric fuel pump while not cranking with the throttle closed and open and it did not have any fuel coming out of the pcv.

Put the plugs back in it, with the fuel pump off, choke on I started cranking with my father in laws finger over the pcv and immediately took the choke off and it fired up! Ran smooth until it ran out of fuel.

Turned the fuel pump on, started cranking again and nothing happened. Held my foot to the floor with the choke off thinking it was flooded and it would spit and sputter and fuel just RUNS out of the pvc valve after my father in law tool his finger off. The more throttle I give it, the more fuel pours out. With no throttle it will drip fuel out while spitting and sputtering. Are there supposed to be some kind of gasket pertaining to the accelerator pump? The TM said only use one gasket for the accelerator pump but it did not have any when i took it apart and the kit did not seem to have one thst fit anywhere. Is it pulling gas past the accelerator pump into the vacuum ports?

[RMS]

sounds like the float is not set right or the fuel pump is making too much pressure, bypassing the check.

with the top off the carb and fuel pump on the gas level in the bowl should be constant if it over flows check the needle and seat

[dozer_xj]

OK the check ball spring between the pump and the jet is supposed to be tapered and I I am pretty sure I used a straight spring thus letting the check ball fall into the spring and letting vacuum pull fuel out.





I think I mixed the accelerator spring up with the high speed circuit spring



The carb is off the truck but havent had time to tear it apart yet.