diagnosing briggs ohv slow cranking

[38racing]

Gee my threads just keep going. I did the engine swap. I did complete head service (funny story to tell separately) and adjusted valves. Intake at .003 low end. I still had slight hesitation of the crank, sometimes. Most of the time it just turned fine and started. Charging voltage high 13 to 14. Battery voltage over 13 with engine off after a cutting session. 12.7 after sitting. But the sometimes hesitate still there. Doing a double check I found that he had crimped end on ground strap and it was slightly loose. So I replaced ground strap and cleaned all cable connections and even decided to put on a new starter solenoid. Debated but did not add the separate relay to eliminate impact of safety switches to the solenoid. Although it might hesitate it never failed to start. Returned it to him. Got a message last night . Won't start. While watching tv I wired up the bypass relay and went over and installed this morning. He had got it started again by charging the battery. battery is new 350 CCA and tests fine. So after the install the bloody thing won't crank enough to start. I took my meter that will check amps on starter cable . Seeing 250. But here's a kicker. While I'm doing my thing he's trying to eliminate air leak on his small generator. I go over to help. I come back and turn the key on the rider and it fires up like there's no problem. Does so several times and then it barely turns. If we try enough we drop the battery below 12.4. If we recharge for long enough it will start. I told him to charge and if starts then cut his grass I'll then bring it back to my place.
I'll recheck the valves and maybe put a dial indicator on to confirm compression bump. I'm puzzled that decompression problem would come/go. Usually it's always there.
As for the starter, we started an old opposed twin mower that I gave him. Seeing 150 amp on the cable. Does the 250 on the starter point to it or could it still be a sign that a wiring or load problem is impacting it. Since it's electric PTO I did check that I can hand turn the deck belt pulley. Going to look at the briggs starter test tech stuff now.

[bgsengine]

Sounds like you may have a bad spot on one of the starter windings , or sticking brushes - might want to try a known good starter , if it solves the issue, take the old one apart and see if brushes are worn , look for burned contacts , ohm out each of the starter windings..

[Arkie]

Sounds like you may have a bad spot on one of the starter windings , or sticking brushes - might want to try a known good starter , if it solves the issue, take the old one apart and see if brushes are worn , look for burned contacts , ohm out each of the starter windings..

Agree:
I've had really good luck with starters from DB Electric.
You can find them on-line or at flea bay and their price is about 1/2 of OEM starters.
I've also had DB Electric starters apart (Briggs type) and they are built good inside, looks like OEM Briggs stuff inside.

If a starter puts it too cranking good I do a amps draw comparison test of the new starter to get an idea if the amps draw went down. I then pull the old starter apart for inspection. Sometimes I will do the inspection first before replacement, but real test is do the replacement.
250 amps for a Briggs starter amp draw is too high, maybe a magnet actually unglued and rubbing on the armature or a shorted armature. (or sometimes one brush won't make and the starter hangs and don't get a good boost start.

I've got all kinds of electrical test eq and sometimes after process of elimination I just have to break down and do a starter replacement.
If the bendix end bushing has any slack is a bad sign. Also if you do a no-load test of the starter and it squalls when you remove voltage, it's squealing because the bushing are very dry and or a piece of magnet or one magnet itself has broke off and rubbing on the Armature.

AT 250 amps draw you are getting close to the starter solenoid contacts welding closed and a constant starter running even with the key off, so keep a heads up. Seen it happen quite often and usually do not know such until the engine is killed.

[38racing]

Thanks. I have a known good starter to try. Had same issue on another friend's ariens and it was play in the end bushing. Just funny that my replacement engine ended up with starting issue like original but hopefully for a different reason.

[38racing]

Would I expect to see higher amp on this starter doing a no load bench test than I'd see doing same test on a good starter.

[bgsengine]

Would I expect to see higher amp on this starter doing a no load bench test than I'd see doing same test on a good starter.

generally, yes. but there can be cases where a starter will bench test fine and then fail on install (example: warped or bent mounting tabs that twist things out of alignment when tightened down... ask me how I know.. hehehe) But generally, even on bench test you would typically wanna see less than 60 amps (usual draw I have seen is more around 30-ish amps, if I recall from trying out a brand new known-good rider, to get some baseline numbers on a variety of tests long ago.

[Arkie]

I'm just speaking from experience here, not from what is listed in a service manual test.

You really cannot trust a bench no load test when a starter is testing intermittently bad on a machine. (especially when cranks good more often than not)
But if you see a no load amps test on the 4 inch area Briggs starters of more than 40 amps it has some concern. When under load just one bad brush of the 4 contacting the communtator causes weak starting torque. High mica between the comm segments can cause weak starter but usually the amps won't be really high.
Typically 30 amps or less on the 4 inch Briggs types no load on the bench from a 12v fully charged battery.

Seems most generally you will visually detect a issue with the Briggs 4 inch starters when doing a internal inspection when one is starting to fail. To aid in re-assembly alignment I place witness marks on each end of the starters and electric motors BEFORE removing the bolts. (and make sure the shaft turns freely by hand as the bolts are snugged up during re-assembly.

I have a growler for testing armatures, but very rarely find a shorted armature communtator on a small engine starter.

[38racing]

ok. pulled off the tarp today. first test was compression. 150 psi. so I check the valves. both at about .012. I know I had them in spec earlier. Don’t know if the friend messed with them . I reset intake to .003 and exhaust at .005. compression still 150. I don't see any bump on the intake like I did before so I'm assuming the acr is done. not sure what I'll do. I take it that aftermarket is real dicey. OEM is about 150 cdn. I have a good running 28 I could put on it or the 28n I have with a hole in the block apparently has the same cam in it.

[38racing]

EDITED:have the engine out but also just viewed a video. This 31 has the oil pump cover so I am assuming it has a pump even though it has no oil filter. edit: correction this 31 with no filter has no pump. Not sure why I thought that I saw a pump cover. Looks like maybe the 28 cam won't work because it won't likely have the slot for the pump shaft. edit: correction. Turns out the donor 28 was a 28p.... labelled vanguard code 96.... and it had an oil filter and pump. Pump was on an adapter and pointed forward although the IPL shows the sump with standard filter mounting base. The cam has the ACR intact. The oil pump drive appears to machined on the end of the camshaft journal, no slot and no give to the pump drive end. It fits in the sump fine. All cam dimensions matched up. Not sure if the new sump gasket will arrive before we take a short trip to celebrate my mother-in-law's 96th birthday

[38racing]

well. cams are not the same. 28 series from 96 has a thicker cam gear piece. height from block side journal to top of gear is same but extra thickness won't let it sit down. it rubs on the crank/balancer face. I discovered this after having problems seating the sump. I pulled open the 94 ohv 28 that I replaced with this 31. it has not oil filter or pump so outer journal matches this time but again the gear is thicker. frustrating is that acr is in tact . it has 30 thou bump and mechanism ok. so the issues with it cranking were likely electrical. did a quick leakdown and it has intake valve leak so can't just throw it back on. looking at a plan c.