Cranks slow

[jeepwatchman]

I have a '94 'Burban w/H.O. 6.5 turbo and lately the truck has been cranking slow after the glow plug light goes out when I turn the key to start. Replaced the glow plug relay the other day, I have Kennedy fast heat plugs, batteries are 1 month old 1000cca@32 deg and 875 cca's. Had the batteries load tested yesterday and they checked out at 11.8 volts after load test. Starter checked out ok. Truck starts, but, it's been cold here and it takes some cranking to start it. It doesn't turn over as fast as it should. I guess my question is...what would cause it to crank kind of slow when starting? Could a bad glow plug suck too muck voltage and make it turn slower? When it does start, voltage comes back up to about 14v according to dash guage. So, any ideas?

[kowsoc]

In the winter months I use a 0W-30 engine oil. It makes a big difference on cold cranking. Other than that I would check for a bad ground or other connection. I have found the grounds on either side of the intake manifold can loosen over time.

[rjschoolcraft]

I use 5w-40 Shell Rotella-T synthetic in the winter. It makes a very noticeable difference in cranking speed. I'd be a little leery of a 0w-30 oil, since I doubt that it meets the diesel specs. But if it works, for you...

Another thing that you can do is to mod the side post battery connections. The article Improved Side Terminal Battery Connections (http://www.thedieselpage.com/members/batterm.htm) is available in the members area. This also made a big difference in cranking speed.

[Marty Lau]

Check all the conections, the piggy back positive will sometimes losen, make sure they are tight. I second the 5w-40w Rotella I been using it for a year plus and it really helps in colder weather.

[kowsoc]

Yeah the 0w-30 is a full synthetic diesel rated oil (exceeds API spec CI). The brand up here is Esso but it is made by Exxon. They also make a 0w-40 that some diesels up here use all season long.

I remember a post a while back by pannhead, same problem. He also said his starter tested O.K. however it turned out to be the problem. Should be easy to find that post. Good luck. smile.gif

[britannic]

Be sure to check all of the grounds at the same time, also pay special attention to the ground to block and make sure the starter is nice and tight. Use an OHM meter to check the resistance from the block to battery. If necessary install an upgraded ground wire or an additional one, so that the batteries can provide maximum benefit.

[moondoggie]

Good Day!

brittanic: Your ohmmeter must be a lot better than mine - mine has 0.1Ω resolution. If battery connections have 1/10 of that, or 0.01Ω, they will drop 2V @ 200A. I have to do this type of resistance measurement indirectly by measuring voltage drops. Fortunately this is pretty easy.

Blessings!

Brian Johnson, #5044

[britannic]

Originally posted by moondoggie:
Good Day!

brittanic: Your ohmmeter must be a lot better than mine - mine has 0.1Ω resolution. If battery connections have 1/10 of that, or 0.01Ω, they will drop 2V @ 200A. I have to do this type of resistance measurement indirectly by measuring voltage drops. Fortunately this is pretty easy.

Blessings!

Brian Johnson, #5044 Measuring voltage is even better! When I was rebuilding my truck before I went out and bought the batteries, I used my ohm meter and continuity tester to check for bad connections.

[ucdavis]

I didn't see cable corrosion mentioned. Old cables sometimes corrode inside the insulation & you can occasionally see that as a bulge in the insulation covering, but the absence of a bulge isn't proof that old cables are corrosion free. A very fine scale ohm meter will probably pick this up (see moon's discussion above) but a new set of cables (if the current ones are old) is a really quick & sure-fire test that doesn't cost much.

[moondoggie]

Good Day!

That's why I like checking for voltage drops: its FREE (assuming you already have a DVM) & it ALWAYS picks up problems like this. The downside is that you need a helper if it's a cranking problem.

Blessings!

Brian Johnson, #5044