mark928gt

Hey Guys,

I just changed out my oil lines on my '89GT a few days ago. Ran the car just for a little yesterday. It started a little funny but then seemed to settle into it's normal idle. When I pressed the throttle everything sounded fine so I shut it off. Thought I would take it out today just to make sure I didn't have any leaks before I put all the bottom pans back on. The car would not start today. Here is what I have checked so far. Any suggestions on where to go from here would be appreciated.

1. Pulled the #1, #5 and #6 plugs to check for spark. Each plug was wet with fuel and each plug sparked.
2. Marked my timing belt and then cranked over the engine (It is just me so I can't watch the timing belt rotate). Timing belt is moving fine (it is 5 yrs old with about 5k on the belt).
3. Checked compression in the #6 cylinder. I got about 120 psi reading but I also did not have a good way to tighten the compression tester into the cylinder really tight. I left it at that because I had compression.
4. Air cleaner looks brand new and there is nothing in the air box.
5. Disconnected the battery for 15 minutes and then tried starting again. No luck. Although it did sputter once which it had not done before.

Thoughts? I did have bad fuel once and had to drain the tank and flush the lines. I rebuilt this motor about 5 years ago (and 5k miles) and it has always run fine. The only time in the last 5 years it did not fire right up was with the bad fuel. I'm leaning toward this again since I filled the car the last time I had it out. I don't really want to drain a full tank of premium fuel if I don't have to.

Thanks.

Shark2626

Which plug(s) had spark? Wet spark plugs indicate no or too little spark, unless they are black with soot (too much gas). Too much gas would tend to point to the dampners. Worst case scenerio... Take the air intake tubes off and inspect the belt the best you can. Never heard of gas that won’t burn, but you’ve been there so it’s a real possibility this time too. Probably nothing, just following the clues on the Internet.

Mrmerlin

Put the plugs back in,
charge the battery with a 6 amp charger not a trickle charger for 4 hours,
get in hold the foot to the floor,
then crank it till it starts.
Please report what you find

Darien

Any lights on the IMS? Nevermind....I see it won't start

mark928gt

Pulling the battery to charge for 4 hrs as Stan suggested. Will report back tomorrow.

Shark2626 - All the plugs I pulled (1,5,6) all had spark.

Thanks guys!

mark928gt

Put the battery back in today. Pedal to the floor and cranked till it started. It took a bit and there was a bit of a white cloud of smoke until it fired. Once it fired (Yay!) it ran rough for probably less than a minute and then settled into a good idle. I let the car warm up good and then shut it off. It started right back up just like normal. I did not take the car out to put it under load.

So, what might have caused this? When I put the battery on the charger last night I checked the voltage and it read 11.8V. Why pedal to the floor to start it today?

Thanks again for the help Stan. I want to understand what happened so I can avoid it in the future.

Mark

Mrmerlin

Hi Mark glad its running based on your report you flooded the engine.
Some time when you start the engine then shut off like if your gonna move the car out of the garage
the richened fuel mixture will foul the plugs couple this with a weak battery and the stage is set for a unstart to occur
The remedy is to charge the battery then hold the foot to the floor and crank it till it starts.
NOTE when you start the engine let it get to running temp to before you turn it off

NOTE also check the vacuum lines on the dampers and FPR for fuel smell as one of these leaking could also be a cause of this issue

mark928gt

Thanks Stan! I will check my vacuum lines to the dampers. I did let the car fully warm up before shutting it off.

Thanks again!

Mark

mark928gt

I wanted to update this thread so if someone else finds the thread at a future date when they are troubleshooting maybe it will be more help to them.

Update: As stated before I got the car running by following Stan's "foot-to-the-floor" and fully charged battery recommendation. Coming out the next day the car would not start again. I just leaned in the car and turned the ignition to make sure I was not tapping the gas at all. I have another car that takes a few pumps of the gas to start so I wanted to make sure I was not doing this without realizing it.

Again, foot-to-the-floor method and the car started. Runs fine. Drove it on a nice loop (50 miles) through the mountains. Car runs normal. Hot restart no problem. Let the car cool down and restarts fine. Next day. No start again and have to use the foot-to-the-floor.

Reading more about the dampers and Stan's recommendation to check vacuum lines. Pulled out my vacuum pump and checked both dampers and the fuel pressure regulator. All three hold vacuum. I checked the vacuum on each for about a minute and all held without any decay. When I pulled the vacuum line out of the fuel pressure regulator the line came out too easy. The others were really hard to get out but this line slid right out. I thought..Aha! this is my vacuum leak. I reinserted the line back into the fitting and left the car until the next day. Same no start the next day. I had more vacuum line and a replacement elbow for the FPR so I changed both of those out. I was encouraged because leaving the car to sit for a couple of hours and then coming back to it, it started right up.

Come out the next day and the same no start situation again. Right now I am thinking I have a very slow vacuum leak that is not holding vacuum over night. Could this be the case? If so, how do I find such a small leak? BTW the fittings and vacuum lines were all replaced new when I rebuilt the engine 5 yrs ago. Everything still looks new.

I'm going to go down in a little bit and check all the vacuum connections I can get to and make sure I don't feel anything else that is "loose". Any other thoughts?

Thanks.

soontobered84

Check your Temp II sensor on the water bridge. I'm not really a fan of throwing parts at a car to see if it will run.
There are plenty of threads about how to check the Temp II.

Or just replace it. They are pretty inexpensive.

mark928gt

Thanks John. I'll do a little digging.

worf928

Sounds to me like you have ‘electrical issues.’ In particular:

- parasitic draw that, overnight, draws down your battery.
- old battery? More than 6 years old?
- battery that has been deeply discharged at least once without then immediately charging it fully
- battery ground strap original?
- engine ground strap original?

mark928gt

Hi Dave,

The car starts each day I go down. It cranks fine and will crank enough to start the car each time. I ran the car again today. The battery is about a year old. Would a weakened battery have enough to crank the car to a start but not fire it right away? Sometimes I have had to crank it for a bit.

One thing I just realized I did not mention earlier. When I first crank the car it has a couple of seconds like it is going to start fine but doesn't. I would say when I normally start the car it cranks a couple of seconds and then starts up. It does the same now, then sounds like it will run for just a second and then continues to crank. Does this point to anything?

WICruiser

Sounds like you have weak spark, rather than no spark and the rich fuel mixture upon initial cranking overwhelms the ignition's capabilities. What is the condition of your caps and coils?

mark928gt

Roger - Caps are new but the coils are original. Maybe an original coil causing weak spark.

Temp II sensor. at 70F both contacts to body measure around 2100 Ohms resistance. At really hot temperature (not quite boiling water because I did not figure out how to hold the sensor in the boiling water and get both of my multimeter leads in the right place) both contacts measured around 500 Ohms. I think the Temp II sensor is ok.

Interestingly when I went to take out the Temp II sensor it was not very tight. I noticed a little shine at the base of the sensor. It was wet with antifreeze. I wonder if the sensor being a little loose did not get a good ground and was not functioning properly. I'm going to put the sensor back in tonight and see how she starts in the morning.