p24-1953 Posted April 29, 2017 Report Share Posted April 29, 2017 Here is what I've got going on. Last week I replaced the gas tank on my truck, while I was at it I fixed a issue of a air/vacuum leak at the base of the carb. I drove it for a few days and it ran great. Two nights ago on the way home while after a sustained cruise on decel I had a loud pop I assumed it was a back fire. Got home let it cool down and went to look for the offending exhaust leak that would cause the backfire. The truck would not start and was very slow cranking. While looking for the root of the problem I left the key on and discovered that the because a piece of trash was in the carb, the float did not close properly and the electric fuel pump fed about two gallons into the manifold. I cleaned the carb, drained the oil, left all plugs out and left it for a day. Tonight I placed a little oil down each cylinder replaced the plugs, and tried to start it. It cranked very slow, still.... I have checked the compression on all cylinders 35 with a slow cranking 6v battery. (90 with a 12v battery.) The distributor is tight and I have a strong spark at each wire. I have tried it with a 6v battery and 12 volt jumper and with the plugs in both turn very slowly. I. Fact there is very little difference. Without the plugs it spins freely and there is a noticable differnce between 6 and 12v The slow turn condition has no change if the coil is on or if it is just turning the engine over. If my timing some how jumped off wouldn't it turn easier when the coil is off because I wouldn't be fighting the ignition. The engine spins very fast when all plugs are removed. If you install any of the plugs it will slow down greatly when that cylinder hits. The starter was rebuilt by a shop recently, but could that be the villain? What could be going on? I have spark, compression and fuel Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted April 29, 2017 Report Share Posted April 29, 2017 Compression really shouldn't change with a 6v compared to 12v IMO, but regardless it sounds like an ignition issue if you have fuel and compression. Is the spark strong or look weak? Any issues with the distributor moving? Quote Link to comment Share on other sites More sharing options...
JBNeal Posted April 29, 2017 Report Share Posted April 29, 2017 check your battery cables 1 Quote Link to comment Share on other sites More sharing options...
p24-1953 Posted April 29, 2017 Author Report Share Posted April 29, 2017 Found out last night that I have good spark. It will jump 1/4" from the lead from to the block. It will also cause you to say not nice things. When you are the shortest path. The cables are good. Checked the timing last night and it still good. 1 Quote Link to comment Share on other sites More sharing options...
lonejacklarry Posted April 29, 2017 Report Share Posted April 29, 2017 I wonder if the "loud pop" is the key. If there was enough gas in the muffler to allow a detonation, there was enough to cause structural internal damage. I'd look for an obstruction in the muffler which will not allow exhaust gases to flow and make the engine turn slowly. Did the truck run any differently after the "loud pop"? 1 Quote Link to comment Share on other sites More sharing options...
Reg Evans Posted April 29, 2017 Report Share Posted April 29, 2017 3 hours ago, JBNeal said: check your battery cables Yes they should be #1 or #0 Quote Link to comment Share on other sites More sharing options...
JBNeal Posted April 29, 2017 Report Share Posted April 29, 2017 With the spark plugs in place, the starter is under full load to get the engine to build cylinder pressure. Slow cranking is indicative of a lack of adequate current for the starter motor to develop sufficient torque to turn the flywheel at the rotational speed required for ignition to be maintained... Incorrect cable size, internal cable corrosion and corrosion at the grounding points can impede current flow. The difference in cylinder pressure readings at different cranking speeds indicates some sort of blow-by, either from inadequately sealing piston rings or valves or both. At faster cranking speeds, the chamber depressurization rate is small enough that the pistons can build up more gauge pressure...think of it as if your rowboat is taking on water: you can bail it out with your hat if ya move fast enough 2 Quote Link to comment Share on other sites More sharing options...
p24-1953 Posted April 30, 2017 Author Report Share Posted April 30, 2017 Guys it is not the battery cables. It has the same 0# cables it had on it last week, this is a truck that is driven weekly. I am thinking the pop was some how related to the starter. I am planning on removing it and having it tested. It was professional rebuilt a few months ago but that doesn't eliminate it. I am also planning on removing the muffler to see if there is an obstruction. On that side. Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted April 30, 2017 Report Share Posted April 30, 2017 If 12v spins faster, then the truck should start...you maybe have multiple issues, but your no start sounds a bit more like internal then electrical. Any chance it popped because your timing chain has jumped? It would still spark, but not at the right time of course. Hope you get it worked out, keep us posted. Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted April 30, 2017 Report Share Posted April 30, 2017 as the pop sounded and the man drove it to the house only to investigate the next day that the crankcase was full of fuel due to leaving the electric pump on...I would still lean toward weak combustion due to loss of lubrications as indicated by change in compression at cranking speeds 6 verse 12 in conjunction with possible splash fouled plugs...while they may spark out off the engine and open to the air, they can foul under compression and not fire. Do change or at minimum blast clean these Quote Link to comment Share on other sites More sharing options...
lugnut123 Posted April 30, 2017 Report Share Posted April 30, 2017 is there any way the engine could have jumped time some where? If it has spark though it should back fire or something. Quote Link to comment Share on other sites More sharing options...
p24-1953 Posted May 1, 2017 Author Report Share Posted May 1, 2017 On 4/29/2017 at 9:57 AM, lonejacklarry said: I'd look for an obstruction in the muffler which will not allow exhaust gases to flow and make the engine turn slowly. Well I tried removing the exaust, and it made no difference. I change the spark plugs, still verrrrry slow crank. I pulled the starter and the rebuild shop said it needed new bushings, I hope that is it but I'm not getting on it. Not for sure what to try next. Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted May 1, 2017 Report Share Posted May 1, 2017 I think it's time to check your top dead centre position and find out if you have a timing chain that has skipped teeth...only thing I can think of, unless your starter is turning at a snails pace Quote Link to comment Share on other sites More sharing options...
lugnut123 Posted May 1, 2017 Report Share Posted May 1, 2017 I got to agree with 4mula-d , Set it on top dead center and look where the roter is pointing.. But it just seams like it should be back fireing or somthing. Quote Link to comment Share on other sites More sharing options...
lonejacklarry Posted May 1, 2017 Report Share Posted May 1, 2017 OK, then it pretty well has to be electrical. If the starter turns out good, I think I would next check and clean all the electrical connections in the starter circuit looking particularly hard at the grounds. Electrical connections, especially ones that handle a lot of current, i.e., starter cable vs. dash light wire, are funny. They work fine until they don't--just like that! Quote Link to comment Share on other sites More sharing options...
lugnut123 Posted May 1, 2017 Report Share Posted May 1, 2017 did you try to spray a little starter fluid down the carby and give it a whirl . If you got spark some thing should happen. A back fire or spudder Quote Link to comment Share on other sites More sharing options...
Brent B3B Posted May 1, 2017 Report Share Posted May 1, 2017 6 hours ago, p24-1953 said: Well I tried removing the exaust, and it made no difference. I change the spark plugs, still verrrrry slow crank. I pulled the starter and the rebuild shop said it needed new bushings, I hope that is it but I'm not getting on it. Not for sure what to try next. man this sound familiar! in April I took my b4d to CA on a trailer... ran great loading it on the trailer ran like poop getting it to the parking spot at the "Q". checked the fuel, charge the battery, checked the spark.... still, no start! it wasn't until I removed the main ignition wire from the starter and ran a jumper wire from the battery to the coil it started.... but I think I have more issues than it sounds like you have. I started it yesterday after making sure the rotor was at TDC and it ran great, then back fired and sputtered, and then ran great and so on...... think I am going to look at a carb rebuild and the valves for me but that freshly charged battery sure made the difference good luck, I look forward to your findings Quote Link to comment Share on other sites More sharing options...
lugnut123 Posted May 1, 2017 Report Share Posted May 1, 2017 (edited) If your carby is a carter D6G1 . the carb rebild kit is a carquest 96 625 or a NAPA 25 500 . Just order two. Most of them old carbs were the same from 39 to 55.about 23.00 $these are the wrong kits for the D6G1 carter carby. Had to order a different kit. Edited May 6, 2017 by lugnut123 Quote Link to comment Share on other sites More sharing options...
JBNeal Posted May 2, 2017 Report Share Posted May 2, 2017 On a totally unrelated note, one way to check the battery cables is to disconnect the battery from the truck, attach heavy duty jumper cables to the starter switch and a cleaned off starter bolt head and see if there is any change in any electrical system performance...I did this on a diesel tractor once to determine that the braided cable ground strap was at fault Quote Link to comment Share on other sites More sharing options...
p24-1953 Posted May 2, 2017 Author Report Share Posted May 2, 2017 Installed the rebuilt starter tonight , installed a fully charged battery and no luck. Still cranked very slow with the plugs in. Next I rechecked the timing. It is set at 4btdc. So it is where it was prior to this all starting. New plugs and I am getting spark. I have fuel and it is visible when the accelerator pump is pressed. I installed the known good working carb off of the running 53. No difference.... Switched out the coil with a known good one. No difference. Removed all plugs , left them connected to the spark plugs and cranked it over with the key on. All 6 arced and 2 ignited the fuel/air mix exiting the spark plug hole. I removed the lead to the starter and used jumper cables straight to a 12v battery to eliminate all bettery cables options. It turned over faster but did not fire. The exhaust is removed to eliminate the chance of blockage on that side, heck I even removed the belt thinking perhaps the water pump or generator had started to seize and was slowing cranking. The entire time tonight when ever the plugs were in I never had one false start, a backfire, it never even seemed like it was trying to catch. I am stumped. What should I try next? Quote Link to comment Share on other sites More sharing options...
JBNeal Posted May 2, 2017 Report Share Posted May 2, 2017 Your plugs may be fuel fouled again and need a good cleaning...also, put the jumper cables on the 6V truck battery not the 12V jumper battery to verify cable performance...it might work better tomorrow after a nap Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted May 2, 2017 Report Share Posted May 2, 2017 You win....I'm stumped...only thing I can think is your intake valves are stuck...but that's far fetched...try some starting down the cylinder, not the carb and try it. Quote Link to comment Share on other sites More sharing options...
lugnut123 Posted May 2, 2017 Report Share Posted May 2, 2017 (edited) man this is a hard one. Maybe pull a tappet cover and see if the cam is turning.and see if the valves are going up n down Edited May 2, 2017 by lugnut123 Quote Link to comment Share on other sites More sharing options...
Brent B3B Posted May 2, 2017 Report Share Posted May 2, 2017 I recently had a 6v battery that was only one year old. it would not start two of my trucks. I took it back to the place of purchase, they tested it and it was fine. they charged it, I took it home still nothing. I had them exchange it for a new one and BINGO both trucks started. (at separate times ) probably not your issue but thought I would mention it. also, I am a fan of removing that ignition wire and jumping the coil.... if nothing else just to eliminate the possibility of an unwanted ignition issue or voltage draw (but I am not a mechanic) Quote Link to comment Share on other sites More sharing options...
Silverdome Posted May 2, 2017 Report Share Posted May 2, 2017 Everyone has mentioned ignition timing. Maybe it is valve timing? Quote Link to comment Share on other sites More sharing options...
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