Engine history:
Full rebuild 18,000 miles ago (over bored with new pistons & valve job)
New glow plugs & wires installed at that time.
This car will sit for 1-2 weeks at a time, I usually only drive it on weekends.
The other day, after sitting for a week, it started normally in the morning. I stopped at a store <1 mile from my house to get a coffee. Came out <2 minutes later and it wouldn't start.
I suspected the fuel solenoid was stuck, because it just started fine just minutes ago from a totally cold engine.
So I checked it and it made a faint clicking when voltage applied.
I cranked and cranked in short bursts until it finally started, with a cloud of smoke from all the unburned fuel in the cylinders.
It idles and runs great once started.
The next few times I drove it there were no problems.
Then I had the same no start problem about a week later, again after starting just fine from a completely cold engine.
I started to suspect some air in the system or faulty glow plugs.
I didn't test actual amp draw, but I know that at least some of the glow plugs are working.....for a quick test I put my fluke meter on the glow plug buss bar and got a big voltage drop for 5 seconds on a cold engine. (from 12.5 to 9 volts, returns to 12 after 5 seconds)
So my next theory is air in the system or injector bleed off....but this theory isn't supported by the fact that it always starts quickly when cold after sitting for a week.
The only consistent pattern for when it wont start is that the engine was warm and had just been running.
Any ideas of what else I can check for? (dont say compression)
Random hard starts mkII
Moderator: Fatmobile
Random hard starts mkII
1991 Jetta 1.6L N/A
Re: Random hard starts mkII
I had the same issue on a fresh rebuild. I swapped over to a Ford solenoid to turn on my glow plugs for like 4 or 5 seconds and never had a problem again. If it is good and hot....no plugs needed. If it is low to moderate warm....it wants a few seconds on the plugs. Runs like a molested gazelle. It will test/try to destroy the ligaments in your shoulder, elbow, and wrist if you try to turn over with a wrench.
Get rid of the glow plug relay system.
Get rid of the glow plug relay system.
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Re: Random hard starts mkII
It might seem like the starter is turning it over fast enough,... but commonly when the engine is hot it's tighter and more difficult to turn.
Next time it happens; unplug the glow plug sensor wire.
The glow plugs won't light up when it's warm,... add a little glow and it should start.
Disconnect power to the pump and crank it for awhile.
Feel for warm/hot cable ends from the battery to the starter.
Feel the starter posts, feel the ground cable ends.
Hot/warm spots means bad connections.
Plan B: get a bosch premium remanufactured starter.
Next time it happens; unplug the glow plug sensor wire.
The glow plugs won't light up when it's warm,... add a little glow and it should start.
Disconnect power to the pump and crank it for awhile.
Feel for warm/hot cable ends from the battery to the starter.
Feel the starter posts, feel the ground cable ends.
Hot/warm spots means bad connections.
Plan B: get a bosch premium remanufactured starter.
'91 Golf gasser converted to a 12mm pump, M-TDI.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.
Re: Random hard starts mkII
Well it happened again today:
Started normally after sitting for a week. Glow plug light came on for 5 seconds.
Drove about 2 miles, parked for half an hour. Came back, no start. No glow plug light. Lots of cranking.
Opened the hood, hooked a jumper wire up to a glow plug and directly battery for about 5 seconds. Got back in, and it started on the first crank.
So Im about 99% sure its the GP sensor or relay. I think the engine temp is just warm enough to prevent the GP's from coming on, but they are really needed ( like Trumper suggested).
Started normally after sitting for a week. Glow plug light came on for 5 seconds.
Drove about 2 miles, parked for half an hour. Came back, no start. No glow plug light. Lots of cranking.
Opened the hood, hooked a jumper wire up to a glow plug and directly battery for about 5 seconds. Got back in, and it started on the first crank.
So Im about 99% sure its the GP sensor or relay. I think the engine temp is just warm enough to prevent the GP's from coming on, but they are really needed ( like Trumper suggested).
1991 Jetta 1.6L N/A
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- Global Moderator
- Posts: 7566
- Joined: Wed Oct 30, 2002 10:28 pm
- Location: north central Iowa
Re: Random hard starts mkII
Just disconnect the wire from the glow plug sensor.
Blue/yellow?
It's on one of the waternecks coming from the head.
The glow plugs will always come on,...
but I still think it's a lame starter or cable connections.
You'll find out when the cold weather comes.
Blue/yellow?
It's on one of the waternecks coming from the head.
The glow plugs will always come on,...
but I still think it's a lame starter or cable connections.
You'll find out when the cold weather comes.
'91 Golf gasser converted to a 12mm pump, M-TDI.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.