cross firing

[chvyboy]

alright so im driving my truck and i begin to notice that my truck is like bogging down and at some points almost dying. once i noticed that i decided to head home to figure this out. im about 15 minutes away from my house and the truck back fires (funny because everyone around ducked because they thought it was a gun shot). but then my truck is having a hard time running. died about 10 times on the way home. i checked the spark plugs and they were all clean, no cuts. has anyone had this problem before?

[coops714x4]

put a new distributor cap, rotor bug and plug wires on it. I would put new points and condenser also.

[chvyboy]

i have electronic ignition, i think it might be a little dirty under the distributor cap. im going to take a better look at it tomorrow. i dont think i have the appropriate spark plug wires. my wires are really long, idk if that has anyhting to do with it.

[1972RedNeck]

Could it be your ignition module?

[chvyboy]

i bought a new ignition module and condenser, lets see how that works

[chopnchaneled]

Well ????? any luck?

[chvyboy]

just got back to the truck today , tried a new coil, new ignition module, and new condenser.... it seems im headed the wrong direction.... now im not getting a spark ive hooked up everything right checked it god knows how many times all i get now is the starter motor and no spark.... i tested all the new parts and everything checked ok. so know im lost because i started this project with a half way running truck and now it cant seem to find out the problem. so i decided to just buy a whole new distributor off summit (lucky enough my good friends at autozone took back the the parts lol) im going to try my luck there and see how everything goes. heres the one i just ordered from summit

[GASoline71]

You could have bought that same distributor from probably any parts store instead of waiting on shipping from Summit.

Did you check to make sure you had a good 12v connection to the distributor? A dedicated 12v wire is needed to an HEI.

Gary

[chvyboy]

summit orders get to my house by the next day so its convenient for me. also yes i checked the 12v wire and everything is good. i thinking it was maybe the magnetic pickup

[GASoline71]

If it was the pickup coil... then the new distributor should alleviate that.

You must be pretty close to Sparks, NV.

Gary

[chvyboy]

San Francisco area. and i hope this works

[GASoline71]

Originally Posted by chvyboy

San Francisco area. and i hope this works

Sparks, NV is where Summits Warehouse is... so it's close enough for one day arrival.

Gary

[WAAF]

eeeek china doll.. carry an extra module with you..

[chvyboy]

i have an extra. always good to have those spare parts

[chvyboy]

well i got the new distributor ten hours after i ordered it and it installed really easy!!! everything was dialed in and i was sure i was going to have a running truck after the new distributor.... gave it a couple cranks still nothing.... checked the spark.... still no spark. so after some exploring i figured out the problem. I installed a kill switch that hooks up to the distributor a while back and found out the switch failed and im running 18 gauge wire when i believe it should be around 16 or 14 correct me if im wrong

[cableguy0]

Your power feed wire to the hei should be 12 gauge. Anything smaller will cause problems. It will over work the electronics because they wont get enough current through the thin wire.

[chvyboy]

im going to try that

[HEI451]

Lower line voltage into an HEI doesn't overwork the electronics in the distributor, it just doesn't allow the system to make adequate spark.

The "condenser" inside a large, coil in cap HEI ISN'T a condenser, it is a different part, a noise suppressor, for AM and CB radio RF noisw reduction. Those HEI's are just fine and happy without one of those in it, and, they can go south, causing problems.

The easiest way nto check the wires for leakage is to run the engine on a very dark night, with then hood up. LOOK, spark jumping/arcing is a dead give away there is plug wire voltage leakage.

Also, wires for the HEI MUST be - magnetic suppression, spiral or "magna" core, and at least 8mm diameter -. Steel/copper stranded spark plug wire just doesn't work well with better electronic ignition systems, and not well with the lesser "drop-in" junk like PerTronix systems.

To check the large cap for correct ignition operation when the power feed to the distributor is suspected of problems, simple check is to remove the power feed wire from the BATT terminal on the distributor cap. Then, use an alligator clip fit primary wire, 14 gauge is fine, from a 12 volt power source positive terminal, either battery positive post, or the large BATT terminal on the rear of the alternator, to the BATT terminal on the cap. Try to run the engine then. Runs OK, NO distributor problems, look to the power feed circuits. Doesn't run good, check the distributor.

Spark plug gaps are critical on all ignition systems, more critical on HEI and drop in systems.

Maximum plug gaps:
HEI - .45
Drop in electronic - .035
MSD - .045
Points - .035
NO MATTER WHO SAYS DIFFERENT

HEI's can develop problems with output and evben running, when their components get dirty. Also, the resistance button under the coil can get degraded, causing the system coil to over work, begin to fail, and take modules out like eating candy. Button resistance is 5,000 ohms MAX. Correct coil install sequence is, cap - button with coiled wire pointing up - rubber insulator - coil. The buss bar under the coil can get corroded, stopping coil grounding and spark, as cam any connector inside the distributor.

Coils do not make over hyped advertized giant voltage outputs unless the system has the drivers to do so, and that is only capacitor discharge systems like MSD. HEI is good for 18,000 to 22,000 volts when the system gets to full operating temperature, NO MORE, NO MATTER THE COIL USED. point and drop in systems make 6,000 volts max, no matter the coil, nor voltage feed used.

Correct mwethod to check both HEI modules and coils IS NO LONGER A REISTANCE CHECK. The only positive tests can be accokmplished at an auto parts store that has a machine that tests the individual components separately, off the distributor. Let the coil or module run, get it to operating temp, and watch what it does. Quick tests are inconclusive unless the part is already stone dead. An HEI coil that is layewr shorting WILL twke module after module straight out dead. This is the reason to keep the coil and module on the test to get them operating temperature hot.

Also, to test the magnetic pickup, use a digital ohm meter. A good pickup will have between 400 and 1,100 ohms resistance at operating temperature, will produce a small voltage pulse when tested by spinning the engine with the starter motor, or, with the distributor removed, and spun over by hand on the work bench. Pickup wires should NOT have continuity to ground, the pickup does not need grouding on either of its output wires. HEI magnetic pickup wires can fracture and lose continuity along their travel as the pickup rotates from the vacuum advance operation. This means the pickup can wortk just fine in one position, but when the vacuum advance is engaged, stop working. Check the pickup while adding vacuum to the vacuum advance.

[chvyboy]

thanks for the help. I actually installed the new distributor and still didnt start checked the 12v line that fed into the distributor and my meter read that it had power... realized that the wire was 18 gauge as well. so i decided to replace it with 12 when i found out that the 18 wire was spliced to the original 12 gauge wire and had fell apart so with the wires all fixed the truck finally runs... i believe that i started checking for problems at the opposite end. but what ever it is the truck runs but needs to be re-timed and the carb is a little out of adjustment.