Notices
928 Forum 1978-1995
Sponsored by:
Sponsored by: 928 Specialists

Engine will not start after top end job

Thread Tools
 
Search this Thread
 
Old 10-16-2020, 12:41 PM
  #1  
scottpeterd
Instructor
Thread Starter
 
scottpeterd's Avatar
 
Join Date: May 2015
Location: Uganda, Baltimore, PNW, italy
Posts: 218
Likes: 0
Received 11 Likes on 9 Posts
Default Engine will not start after top end job

So, engine is in and I am trying to start.

Timing belt is new and timing has been checked

we have spark, and the rotor is lines up to #1 at TDC.

Fuel pump is running, plenty of fuel pressure when checked at the input to the fuel distributor and the feed to the WUR.

when I disconnect the hard fuel line connection to the #1 cylinder, I get a strong flow of fuel when cranking the engine, but only if the vacuum plate is depressed. When it is not depressed, there is no fuel flow.

Is there a timing procedure to follow with the fuel distributor?

Old 10-16-2020, 12:58 PM
  #2  
soontobered84
Rennlist Member
 
soontobered84's Avatar
 
Join Date: Mar 2002
Location: Texas
Posts: 5,971
Received 280 Likes on 197 Posts
Default

Post a photograph of the the harmonic balancer at TDC. It is very easy to put the HB on backwards. If this is what happened, you can have spark, fuel and compression, but the spark won't happen at the right time.
Old 10-16-2020, 01:08 PM
  #3  
scottpeterd
Instructor
Thread Starter
 
scottpeterd's Avatar
 
Join Date: May 2015
Location: Uganda, Baltimore, PNW, italy
Posts: 218
Likes: 0
Received 11 Likes on 9 Posts
Default


Old 10-16-2020, 01:33 PM
  #4  
hacker-pschorr
Administrator - "Tyson"
Lifetime Rennlist
Member
 
hacker-pschorr's Avatar
 
Join Date: Aug 2001
Location: Up Nort
Posts: 1,558
Received 2,176 Likes on 1,230 Posts
Default

Did you replace the green wire? If so, how long ago did you buy it?

Might seem like a silly question, but just last week I was helping a friend with a 930 and it had one of the green wires with reversed polarity installed. He replaced the green wire and it wouldn't start, we figured out some previous mechanic flipped the connector in the harness to compensate for the reversed green wire. Either that, or there is once again a batch of those being sent out with reversed popularity.
You'll have spark / fuel but the timing will be so far off, it won't start.

Do you have an adjustable timing light?
Old 10-16-2020, 02:12 PM
  #5  
scottpeterd
Instructor
Thread Starter
 
scottpeterd's Avatar
 
Join Date: May 2015
Location: Uganda, Baltimore, PNW, italy
Posts: 218
Likes: 0
Received 11 Likes on 9 Posts
Default

Green wire has about 25 miles on it. Replaced just before it went into the shop.

we have great spark. Checked at the coil, the dizzy and one of the plug ends.

We just found a fair amount of fuel in the cylinders. Maybe from cranking for a while.

But have also found fuel in the valley of the block. Suctioned it out. Cranked the engine for
about 30 seconds. More fuel. No obvious leaks
Old 10-16-2020, 02:16 PM
  #6  
scottpeterd
Instructor
Thread Starter
 
scottpeterd's Avatar
 
Join Date: May 2015
Location: Uganda, Baltimore, PNW, italy
Posts: 218
Likes: 0
Received 11 Likes on 9 Posts
Default

I also put on a new 14 pin connector. But was very careful about the positions of the wires.

is there a key wire there? I know #14 has the bypass to put 12v at the ignition coil for starting.

The others are oil sensors, and the alternator sub-loom. The #1 is the blue wire going to the alternator. I am not sure what function that serves, except possibly for the dash charge light.

Old 10-16-2020, 02:18 PM
  #7  
scottpeterd
Instructor
Thread Starter
 
scottpeterd's Avatar
 
Join Date: May 2015
Location: Uganda, Baltimore, PNW, italy
Posts: 218
Likes: 0
Received 11 Likes on 9 Posts
Default

We have not checked timing with a light, as the mech says the engine isnt turning over fast enough.

But I checked it statically, and found it was off. So pulled the dizzy and oriented it correctly

And the car was running with the new green before it came in.
Old 10-16-2020, 02:25 PM
  #8  
soontobered84
Rennlist Member
 
soontobered84's Avatar
 
Join Date: Mar 2002
Location: Texas
Posts: 5,971
Received 280 Likes on 197 Posts
Default

Originally Posted by soontobered84
Post a photograph of the the harmonic balancer at TDC. It is very easy to put the HB on backwards. If this is what happened, you can have spark, fuel and compression, but the spark won't happen at the right time.
Well, it doesn't appear to have that issue. HB appears correct.
The amount of fuel in the cylinder would seem to indicate that the engine is flooded. Remove the fuel pump relay and crank the engine. Does it try to start after the extra fuel is pushed out of the cylinders?
Old 10-16-2020, 02:36 PM
  #9  
GregBBRD
Former Sponsor
 
GregBBRD's Avatar
 
Join Date: Feb 2005
Location: Anaheim
Posts: 15,230
Received 2,474 Likes on 1,468 Posts
Default

If you have fuel, and you have spark at the spark plug end of the plug wires:
Remove #1 spark plug. Put your finger over the spark plug hole in the head. Rotate the engine, by hand, until you feel the compression stroke (air pushing out past your finger.) Continue rotating to TDC. Remove distributor cap. confirm the rotor points towards #1 spark plug terminal, in the cap/caps.
Old 10-16-2020, 02:50 PM
  #10  
scottpeterd
Instructor
Thread Starter
 
scottpeterd's Avatar
 
Join Date: May 2015
Location: Uganda, Baltimore, PNW, italy
Posts: 218
Likes: 0
Received 11 Likes on 9 Posts
Default

Greg,

That we have done. Everything is correct.

Reached in the bore with a piece of paper towel. Can out w about 1/2 in of fuel.

pulling all the plugs to air out the cylinders. Will crank with FP disconnected

But we just groke the plug end on #4 wire
Old 10-16-2020, 03:29 PM
  #11  
scottpeterd
Instructor
Thread Starter
 
scottpeterd's Avatar
 
Join Date: May 2015
Location: Uganda, Baltimore, PNW, italy
Posts: 218
Likes: 0
Received 11 Likes on 9 Posts
Default

Update.

checked with a timing light. Showing 50btdc at cranking.

pulled dizzy and timed so it is showing 30 BTDC at cranking
Old 10-16-2020, 03:57 PM
  #12  
scottpeterd
Instructor
Thread Starter
 
scottpeterd's Avatar
 
Join Date: May 2015
Location: Uganda, Baltimore, PNW, italy
Posts: 218
Likes: 0
Received 11 Likes on 9 Posts
Default

Checking voltages on the ignition coil.

When the ignition is on, but not cranking, these are the voltages (referenced from ground) on the ignition coils: 2.5 on the negative, 4.5 on the positive

When cranking: 3.5 on the negative, 6 on the positive

i would not have expected any voltage on the negative.

Old 10-16-2020, 04:49 PM
  #13  
GregBBRD
Former Sponsor
 
GregBBRD's Avatar
 
Join Date: Feb 2005
Location: Anaheim
Posts: 15,230
Received 2,474 Likes on 1,468 Posts
Default

Fuel distributor piston stuck at full travel?
Cold start wired so that it sprays all the time?

At any rate, your engine is not very happy with what you are doing.....

Pull all the spark plugs and crank the engine over, with the fuel pump fuse removed. Change the oil and filter.
Squirt some oil down the spark plug holes, crank the engine over to get some oil on the cylinder walls.
Pull all the injectors out of the manifolds and hook everything up. Spray the injectors into containers and see how much fuel they are delivering.
Old 10-16-2020, 04:54 PM
  #14  
PorKen
Inventor
Rennlist Member

 
PorKen's Avatar
 
Join Date: Sep 2002
Posts: 10,148
Received 389 Likes on 218 Posts
Default

Originally Posted by scottpeterd
pulled dizzy and timed so it is showing 30 BTDC at cranking
Specification is 30° @ 3000 rpm... not cranking
Old 10-16-2020, 06:53 PM
  #15  
khalloudy
Rennlist Member
 
khalloudy's Avatar
 
Join Date: Aug 2005
Location: Riyadh, KSA
Posts: 1,306
Received 147 Likes on 87 Posts
Default

You have compression
You have spark
You have fuel pressure
Are the injectors spraying fuel?
MAF connected?
LH Working?
EZK Working?
Also one silly one I had to deal with before was the Temp Sensor II being broken and hence the car would not start before. Check its resistance.
Did you check that the computers are getting the data? Plug a Theo Diagnostics tool or similar to check all information is reaching the LH and EZK.



Quick Reply: Engine will not start after top end job



All times are GMT -3. The time now is 03:46 PM.