DONR

I have been trying to figure out what is wrong with my 468 engine. New Starter, New Battery, checked battery cables and grounds. I have an MSD ignition system and MSD fuel injection.
It turns over very slow maybe a 1/4 turn then like it locks up. I took all the spark plugs out and used a remote starter button and the engine turned over pretty fast. The engine has about 5,000 miles on it.
I did take the valve covers off and checked for a broken rocker arm, but all was good. When I put the plugs back in same thing again. Turns over slow maybe 1/4 turn. When I turn it over with the ignition switch same thing.
checked the voltage down at the starter and it reads 13.3 volts. Same as what voltage the battery shows.
Any help would be much appreciated.
Thanks!
Don
Well I appreciate everyone's input on my issue. What stumped me was when I read the voltage at the starter when I turned the key on my voltage was ok.
It turned out to be my ignition switch.

leif.anderson93

Did you check the voltage at the starter under load?? Get down to your starter with a voltmeter and have someone turn the ignition key for you...then see what the voltage drop off is. If it reads less than 9 volts with the ignition key turned to the "start" position, you have a bad/internally corroded cable.

R66

Timing?? Pull the coil wire and try cranking it. If it cranks over, you may have too much advance timing.

65GGvert

or plugs miswired

66jack

is it a stock starter...you might have too much compression for the starter....

Westlotorn

Simple work arounds, add a second ground from the battery to your engine block, a jumper cable can do that for you. Second is harder to test, add a jumper cable from the battery to your Pos wire at the starter. A jumper cable wire is not a good as the battery cables but if you see your engine spin faster you isolated the problem to the cable either Pos or Neg.

There is much less load with the plugs out but it is good to know the engine spins free, rules out a lot of things. Having wire crossed can slow the starter to almost nothing but at least in cases I have seen you can turn it over, maybe not as fast but they usually turn. When did this issue start happening? Any other work done at the exact time it started?
Mark

DONR

I will try and answer all responses up to now.
1) I have not checked the starter under load. Both cables are fairly new. Will do that tomorrow.
2) This started all of a sudden. I drove it about 10 miles and shut it off. When I got in to crank it. It barely turned over. I tried again and it cranked so I drove it back to my shop
with no issues until I shut it off to raise the door. It eventually started and I drove it in and put it on my lift. A few days later I went to my shop and tried starting it. That is when it
started turning real slow 1/4 turn again then acting like it locked up. It has been running fine until this started.
3) Plugs are not miswired. Was running fine until this happen all of a sudden.
4) It is a GM High Torque Mini Starter. Before I changed it out I had a MSD mini starter. Had this starter on when this started acting up.
5) I did add another ground wire from the battery to the engine. No change. I have not run a jumper wire from the positive side of the battery to the starter yet. Will do that tomorrow.
I appreciate all of the input so far.
Don

thoyer

As has been mentioned, measure the voltage at the starter when cranking. Doubling up on the ground cable won't help if the problem is in the positive cable.

Big block starters are notorious for heat soak - possible install a heat shield.

Do you know what the compression is?

In our racecar I had 13.5:1 compression and used one of those mini starters but also bumped up the starter to battery wire gauge along with the ground lead size.

Tom

jim lockwood

A lot of what you are describing is consistent with what results when fuel siphons into the engine, filling a cylinder with fuel. That makes rotating the engine impossible without bending a rod.

I have no idea if that's possible with the aftermarket fuel injection on your engine, so take this for what it's worth.

DansYellow66

If he took all the plugs out and the starter spun it over fast then, it would seem that if a cylinder or two were full of gas, fuel would have been shot out of the plug holes - enough to be obvious. Seems to be some sort of starter motor weakness/issue to me but not exactly sure what. Can you go back to the MSD starter?

jim lockwood

Your point is logical and I don't know if fuel siphoning is even possible with an aftermarket EFI system. Still, his symptoms are consistent with that problem..... particularly the fact that the engine spins easily with the plugs out.

But to your point.... I once had a Rochester FI unit leak fuel into the engine of my car. I knew that had happened when I heard the starter go "Unnnnnh" when it hit one particular cylinder. Yet, when I pulled the plugs to clear the engine, I never saw any fuel come out.

Make of that what you will.

R66

Maybe battery cable terminal or corroded cable inside of the insulation. Just more guesses. Also, with the MSD ignition, it may advance and retard timing to support the fuel injection. One might want to do some troubleshooting of the MSD electronics.

phil2302

As mentioned above a fuel hydrolock is a remote possibility.
Check to see if fuel comes out of a cylinder when cranking the engine with the plugs out.
Also check your oil for fuel. If a cylinder is full of gas your oil should be greatly contaminated with it.

jforb

Stock large old fashioned GM starters start big blocks just fine for me, and have for decades. As long as they're in good condition, and the battery cables are in good condition, and the battery is in good condition.

After you try to start the engine, use your IR temperature gun to check the temperature of every high current connection in the system, including the ends of all the battery and ground cables. Resistance makes heat, if one of them is bad then it'll get hot.

Tell us about the battery.

Tell us again about the starter, and it's mounting bolts. If you have a GM high torque starter that was used on production vehicles 20-25 years ago, they take special bolts with a metric shank and US threads, some folks don't know that.

DONR

The compression on the engine is only 9 1/2 to 1.
Jim brought up a good point. I did drain the oil and it did have a gas smell. What threw me was that no fuel come out of the cylinders when I took the plugs out and cranked it over. The dip stick was not show overly full.
I thought maybe it was from me trying to start it so many times and fuel leaked down the cylinders to the crankcase.
The GM starter come with new bolts. The battery is a new high cranking amperage battery.
When I go to the shop today I am going to disconnect the fuel line. When I go to turn the key over I hear the fuel pressure build up then shut off before cranking.
Thanks again for all of the input.
Don

thoyer

Did any of the plugs look wet when you removed them? Jim may be onto something..

Keep in mind though that cranking with plugs installed vs cranking without plugs installed are two different current draws on the battery. Battery / cables may support no plug cranking but may struggle when the plugs are installed and more current is needed to overcome the compression.

9.5:1 should easily crank with a standard starter - no need for the gear reduction types which are typically used on much higher compression builds.

Fun stuff - looking forward to hearing what the cause is

Tom

Westlotorn

If fuel leak is suspected do not add stronger wires or anything else till your fuel issue is ruled out. You are basically hydro locking the engine at that point so rule it out before trying other starter enhancements. Hydro locks are known to Bend connecting rods so be careful.

DONR

I ran a couple more test today.
1) I have not checked the starter under load. Both cables are fairly new. Will do that tomorrow. Did this today. There was no load drop during cranking.
5) I did add another ground wire from the battery to the engine. No change. I have not run a jumper wire from the positive side of the battery to the starter yet. Will do that tomorrow. I did this today and still the same problem.
If it was hydro locking with fuel would fuel leak past the rings? If it sits over night I would think it would try and crank more than a 1/4 turn before hydro locking again.
Still stumped!

jim lockwood

Leakage past the rings is likely. No ring could seal perfectly. Regarding sitting overnight, I assume that you mean if ring leakage happens, the cylinder(s) should be empty? That would depend on the available supply of fuel and whether it could leak into the engine faster than it could leak by the rings. No way to know that one.

Westlotorn

The rings will try hard to seal the cylinder but ring seal is dependent on oil on the ring face, gasoline will wash away that oil so ring seal is diminished and you will have more fuel reach the oil. It will be a very slow leak but it will leak and some will evaporate. I am gathering the engine has an aftermarket fuel injection on it? Does the system allow you to do a fuel injector pressure drop test? Common test available for most FI cars today. This test would allow you to see if your injectors are holding pressure or leaking into the cylinders.
Even if it does not have a pressure drop feature you could examine the whole system by hooking up a fuel pressure gauge and watching what happens after you turn off the key. A good system should hold full pressure for several minutes and then slowly lose the pressure over time.