Carburetor headache

[tom'sB2B]

My summer project has been to pull the front sheet metal off my truck and clean the engine and replace the gaskets, paint, etc. I'm almost done putting things back together and I have learned quite a bit through the whole process. I'm now at the point to where I'm trying to get it started and I'm running into one issue after another and I think so far I've been able to solve them. But now I've run into a problem with my carburetor and I'vefinally relented into asking for some help. I think my carb is putting out too much gas. When I try to start it backfires up through the carb. When I take the carb off, there seems like an excessive amount of gas sitting in the bottom of the intake. Now let me tell you what I've done.

 

1. Cleaned and Rebuilt carb..including new accelerator pump plunger check valve balls and gaskets

2. New needle, put in the right way

3. Measured float height... 5/64 inch from to of the bowl

4. Several adjustments of idle mixture screw starting at 1 1/2 turn out

5. Original fuel pump which worked fine before I started this project.

 

I also checked the timing several times using TDC on cylinder 6. My distributor is indexed at 7 o'clock. I have my plug wires lined up in the correct sequence 153624

 

Its probably an easy fix, but I can't see what I'm missing

[DJ194950]

Sounds like timing!

A timing light hooked on #1 cylinder. wire and light on timing mark should tell the story.

 

Point gap set properly? double check and pull a plug-spark strong and blueish?

 

DJ

Edited July 3, 2014 by DJ194950

[Merle Coggins]

Did you mess with the distributor when you had everything apart? It sounds like a timing issue to me too. You can use #6 wire or #1 wire to check the timing since both plugs fire at the same crankshaft position. They just alternate every other revolution. It's possible that you are 180 degrees off on the distributor. To double check it remove #1 spark plug and bump the starter with your finger over the plug hole until you feel compression. Then hand crank the engine until the timing marks line up. At this point the rotor should be pointing to the #1 plug wire.

 

Merle

[tom'sB2B]

I checked and adjusted points.

I checked the timing several times using a small dowel rod down the #6 port until I found TDC ( which also lined up with timing marks). While doing so I watched where my distributor was(which is about 7 o'clock) and set my plug wires accordingly. I will recheck timing again. Maybe I'm going down the wrong path with my carb thoughts, but I'm hung up on the pool of gas sitting at the bottom of the intake. It just seems like I'm drowning it.  Is this normal?

[Young Ed]

Check your float for a leak.

[Merle Coggins]

It could be flooded just from the multiple attempts to start it.

You did good to find top dead center, but you also need to determine if it is on the compression stroke or the exhaust stroke. Remember 1 and 6 are paired. Both reach top dead center at the same time but one is on compression stroke and one is on the exhaust stroke. Spark must happen on the compression stroke. If you are sparking on the exhaust stroke it will not start.

 

Merle

[Merle Coggins]

Also, have you checked the timing with a timing light while cranking? Maybe you're just many degrees too far advanced or retarded which will hinder starting.

[tom'sB2B]

Ok. So how do I find out whether I'm on an exhaust stroke or a compression stroke? I will check my float again too and go buy a timing light

[Jeff Balazs]

Tom;

Probably timing but there is one thing on the carb you could check. Take a close look at the step up piston to see if it is hanging up. These 60 year old carbs seem to develop a bit of roughness in the chamber the step up piston rides in......can prevent the step up jet from working properly. If it is stuck in the up position it will run way too rich. Also if you did not use the correct gasket at the base of the carb it will block the vacuum to the step up and do the same thing. The correct gasket has slots that allow vacuum from the manifold to go through a small hole in the base of the carburator.

 

Hope this helps, Jeff

[NiftyFifty]

You weren't 180 out when you dropped in the distb right? Needs to be on the compression stroke on 1. I also find some of these new carb kits aren't worth a darn. I've put two in my Massey Ferguson 165 this year and neither one will run the tractor right, but both caused different issues so I know its the kit, as the tractor ran fine before, it just dripped gas. I'd live to find a replacement, but not for $500

[ledfootslim]

My 48 Desoto backfired terrible when I first got her started back up, but after a week of starting it up, letting it run a while as I tinkered with various stuff.....it stopped!

[tom'sB2B]

So, I guess my next step is to pull the plug on #6 and watch when the exhaust port is open and try to retime everything. I guess I didn't understand the term "180 degrees off". I may have been chasing my tail this whole time. At least its easy to work on with the hood and fenders off.

[NiftyFifty]

That's the best way, I actually pull all the plugs and then put my thump over #1 and tap the starter until I feel the compression and then set the crank to TDC, but you have to have someone with a light touch on the starter pedal, or someone to turn the crank at a decent rate for you... But my plug was seized in the head so I had no choice with my original engine.

[Don Coatney]

I posted this in another thread a few days ago.

 

 

My car had been running really good until I went for a drive yesterday. My engine developed a slight irregular misfire with no repeatable pattern. I suspected an issue with adjustment of my dual point setup so the first thing I did was pull my distributor. I set up my bench test using an electric drill, power supply, and test coil. I found a slight variation in dwell angle. I made a very slight adjustment in point gap and corrected that issue.

 

Prior to pulling the distributor I brought the engine to TDC and noted the rotor position. Having made the slight point adjustment I re-installed the distributor and positioned it very close to the same position it was in when I removed it. I made an attempt to fire the engine and it was a no go. I made attempts to fire the engine with my remote starter button and a hot wire under the hood while turning the distributor under the hood and it was all a no go. I connected my timing light while cranking the engine with the starter and found my timing was a good way off from TDC. So I brought the engine to TDC using the starter motor. I pulled the plug wire from #1 spark plug and connected it to a spare plug sitting on the head. I then (without spinning the engine) moved the powered up distributor until I was getting spark exactly at TDC correctly static timing the engine.

 

As I had been spinning the engine a lot with no fire I suspected my plugs may be fowled so I removed them and sand blasted them. While the plugs were out I also used an air gun down the plug holes to clear the cylinders of any flooding. Reinstalled the plugs, hit the starter button, and the engine fired right up. I then used my timing light to dial it in.

 

So my point being correct engine timing is a very small window. If you take the time to insure your engine is correctly static timed and all other system problems are corrected the chance of starting is greatly improved.

[tom'sB2B]

O.k. I think I'm on the right track. I will use the old finger method on the number one hole (  ) tomorrow and hopefully will get my timing sorted out. I've been reading several threads on the topic of timing and compression and it doesn't take long for my eyes to glaze over. I've learned a lot though.

[tom'sB2B]

Thanks for reposting that Don. I will try again tomorrow and hopefully sort it out.

[tom'sB2B]

I got it running. The timing was definitely off. After a couple of gunshot backfires and shocking myself a couple of times, I figured it out. I pulled plug #1 and found TDC on the compression stroke. Then, with the plug out, I rotated the cap until I got spark with the number one spark plug. I had to adjust the backing plate on the distributer to where I could adjust it. I must have been off a couple of teeth when putting my oil pump back in.

It still idles a little rough, so I will make some adjustments this weekend using a timing light and a vacuum gauge.

Thank you all for your help....Time for a beer!

[greg g]

most distributors  have another bolt on the clamping piece that will allow you more adjustment of timing if you need it.