Cold start issue

[96ccdd]

I know this many have been covered before in one fashion or another, but I’m lost. Last year my 96 Suburban started have cold start problems, so I figured that with 160k on the clock, I figured it was time to replace the glow plugs. With that done starting did improve just a little but I dealt with it. Now this year cold starts have gotten worse, if the truck sits for more than about 6hrs not plugged in, it takes several cranking cycles before it starts. Just last week I pulled it in the garage to change the oil and put a manual glow plug circuit in, which works well. After sitting in the garage for 4 days, I let the truck go through its normal cycle and then extended the glow time manually. After 5 tries and the truck not starting, I plugged the block heater in at about noon. This morning @ 4:30am I went out, let the truck cycle once and it started right up. I check and the glow plugs are getting 12vdc. I’m totally lost as to why it will not start unless it has been plugged in. I know the injectors and/or IP pump may be an issue now that the truck has 180k on it. I would have thought that using the manual glow pug control would have been just as good as plugging in the block heater.

[Chief919]

What brand of glow plugs, and have you tested them for resistance?

I have seen some cheap off brand glow plugs that barely got warm, and never hot.

[96ccdd]

I bought them from S&S. What type of resistance reading should each plug have ?

Thanks

[Chief919]

I bought them from S&S. What type of resistance reading should each plug have ?

Thanks

.8-1.2 ohms each, when cold, is nominal. Under 2ohms is usually ok.

No resistance, a high resistance, or an open circuit are bad.

To see if the ones you got are good ones, pull one out, complete the circuit by holding the thread against the block, and see if it gets hot when you cycle them. You can also use a 9v battery and they should get fairly warm from that.

[DennisG01]

I bought them from S&S.

But, what brand are they? Are they a "quick heat" type?


Resistance should be minimal -- < 1.5 ohms.

Check resistance between blade (take power wire off, first) and ground/glow plug casing. You could also use a test light wired from B+ and touch each glow plug spade (again, with power wire removed).

[96ccdd]

They are " SSDiesel Supply "Instant-Heat" Glow Plug Set for all 6.5's ".

[JohnC]

I'd test them. There have been some bad batches of "quick heats" from more than one vendor. The fact that the block heater helps a lot indicates it's a heat issue.

[96ccdd]

Thanks for everyones in put. I started removing them one at a time and testing. The first one on the drives front tested good 1.19 and glowed very nice. The other 3 are in the K ohm range. I will be ordering a new set tomorrow, should I get another set of quick heat or G-60's ? Thanks again.

[janderson]

Excessive on time by using a manual control may burn out the glow plugs.
96ccdd - How long did you extend the on time?

[DennisG01]

Walt will warranty them, but in the long run it's not worth the hassle. I've been there. He told me "I'll warranty them, but this is odd because I sell 1,000's of these a week and very rarely do any come back". I find that hard to believe. Just get a set of 60's.

[Robyn]

Another often overlooked issue with these little creatures is the injectors.
When they get some serious time on the clock the pop pressure fall off and they start peeing a stream.
Now the ideal is to have a nice cone of fine fuel mist land right on the red hot glow plug.
If the pop has fallen off and the injectors are peeing off into a corner the cold start is going to be slow and balky and the smoke when it does light is gonna take care of a swamp full of skeeters.

Do check your glow plugs to be sure they are good, but also yank the squirts and get them checked.
A fesh set of squirts and good plugs and the 6.5 should bang right off after little more than a couple seconds on the starter.

My 94 just bangs off after the rebuild. The squirts were just terrible in that thing. I reused the original glow plugs that I got with the truck and I have no idea how many miles are on them.

They all glowed good so back into the fire they went.

Its amazing how much of a difference the spray pattern and such makes in the start up process.

Warm weather or heating with the block heater will mask a lot of these symptoms.

Also I have found that with the use of the block heater in really cold weather that starting can still at time be a bit bumpy. The ECT sensor thinks the engine is warm so the timing does not advance and with very cold temps the starting can be a tad cranky.
Unplug the coolant temp sensor if this is an issue and then plug it back in once the engine is running.
The ecm thinks its like -30F and gives the thing full advance on the pump.

Just a trick.
Best thing is to fix the cause.

Top things to worry about.
Good cranking speed
Good glow plugs that glow from the middle to the tip and nice and red.
Good spray patterns from the squirts

With these things right the little creature should snap right off.

Give the squirts a look.

Robyn

[96ccdd]

Well I just ordered a set from JK, hopefully I will have them by the weekend.

Robyn I have a question. In warmer weather, 60F+ my truck surges or bucks when I get over 65 mph. Would this be the injectors also or the IP itself ?

Thanks