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hard start

1994ch

1994ch

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Location
South Carolina
So for about a two months now I have been chasing a hard starting problem. It cranks fine, and fires on at least several of the cylinders but it will not catch and run. For a while I thought I had a leak that was letting air in so I have replaced the rubber fuel lines. That seemed to fix the problem for about a week but now it is starting to act up again but randomly. Sometimes it fires right up with just a second or two of cranking and other times it won't start. Sitting overnight does not seem to be worse than starting up after a quick stop. I did notice that the fuel shut off solenoid seems to be a bit loose (not loose in the IP but there is some wooble in its assembly). Another weird thing is that if I open the bleed valve and crank it with it open it will often fire right up. This makes no sense to me because it seems that more pressure on the inlet side of the IP would help.......
Also if the shut off solenoid is going bad could it cause these systems?
Does this still sound like air in the system or an electrical or internal IP issue?
Thanks for any ideas,
Charles
 
Get a clear line on the ip return. It's 1/4" and you need just under 6". Watch for bubbles to indicate if you are sucking air.

Also when it first starts go out and crack injector line nut to ID which cylinders & see if bleeding clears it up right away.

Other than that you could have some bad glow plugs. IMO, if a couple are bad- swap them all.
 
This morning it would not start until I unplugged the coolant sensor then it fired right up. So maybe that was the problem because it seems I have read somewhere that a bad sensor can cause a hard start.
 
"I did notice that the fuel shut off solenoid seems to be a bit loose (not loose in the IP but there is some wooble in its assembly)"

Replace it as it shouldn't wiggle. Or go to a hardware store and get a faucet thread plug and just plug it's hole on the IP. (leave it's guts plugged and zip tied to the engine to prevent a code.) It's about useless except for key off on a rare complete IP runaway failure. The ECM won't shut it off on runaway - you have to.

Any air leaks like I suggest you have above will let the system loose prime. The hit and miss while purging air will break the starter. Fix it ASAP and quit driving it till it's fixed.

Note last time I had starting issues like this my cheap China injectors were sticking open at 30K miles. Just saying starter replacement isn't fun.
 
I can get my starter out in about 20 minutes. On my IP comment I have a thread here somewhere called hard cold start. Turned out to be the IP.
 
Well I have tried unplugging the coolant sensor a few more times and it did not help, so that first time must have been coincidence. Yesterday I tried a few times to start it and it would not (probably 40 degrees) Then this morning I went out (27 degrees) and it fired right up. I can't seem to find a rhythm to it so I am really stumped. I have cleaned the grounds, but now I am thinking about replacing all of the battery cables.

Are there other ideas of where a bad electrical connection could cause this? It cranks at a good speed, fires very consistently, but just won't catch and run.

Thanks so much for the help and ideas
Charles
 
As mentioned above: the GM manual says to check for air first...
 
I talked to someone who said that a bad optic sensor can cause this type of problem. And I was thinking of checking the harness as well. The radio noise filter looks pretty rough, does any one know if / where these can be found? I looked at Rockauto and could not find it.
 
1994ch said:
I talked to someone who said that a bad optic sensor can cause this type of problem. And I was thinking of checking the harness as well. The radio noise filter looks pretty rough, does any one know if / where these can be found? I looked at Rockauto and could not find it.
Click to expand...
Just remover the filter, throw it away and plug the harness directly into the injection pump.
 
When cleaning grounds a few weeks ago I noticed that the underhood light seemed brighter with the left battery than the right battery. So last night I swapped batteries left to right and it has started four times in a row so far without a problem (before it was rare for it to start without a fight). So I am thinking that something about the bad battery was acting like a bad ground and having the better battery closest to the starter and computer connection works a little better? I am thinking new batteries (with the post instead of the lousy side terminals) and all new cables are on the horizon.
 
I am still not sure that it is the main problem though because I have started it before (a few years ago) with batteries so weak it would hardly turn over but it still stumbled to life.
 
100 RPM Minimum cold and 150 RPM hot is what it takes to start the engine. Anything slower is just dumb luck if it starts. Weak/bad batteries can brown out or black out the ECM when cranking so that it can't do it's job and - no fuel.
 
1994ch said:
When cleaning grounds a few weeks ago I noticed that the underhood light seemed brighter with the left battery than the right battery. So last night I swapped batteries left to right and it has started four times in a row so far without a problem (before it was rare for it to start without a fight). So I am thinking that something about the bad battery was acting like a bad ground and having the better battery closest to the starter and computer connection works a little better? I am thinking new batteries (with the post instead of the lousy side terminals) and all new cables are on the horizon.
Click to expand...
The side posts are fine with good cables and the Allen screw battery bolt mod. I always get dual post batteries with side and top posts

Get yourself a battery load tester. They are a cheap diagnostic tool. The Harbor Freight el cheapo is supposed to work pretty good. I got a couple of name brand load testers pretty reasonable off of Ebay

I always test with the batteries hooked up first. If they fail that, then you know you need batteries so there is no sense in disconnecting and testing them properly.

To properly test the batteries, disconnect them, Charge them, let them sit at least 2 hours and then load test them one at a time.
2 hours is the longest it has taken for me to have a bad battery SHOW BAD. Sometimes a bad battery will test good until after it has sat a bit, after charging
 
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Well it has been a week and I have driven it every day with no issues after swapping batteries right to left.
 
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