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

Pre-start cranking noise?

Thread Tools
 
Search this Thread
 
Old 06-05-2015, 11:21 AM
  #1  
BigAl1
Thread Starter
 
BigAl1's Avatar
 
Join Date: Jul 2010
Location: SW Ontario, Canada
Posts: 692
Likes: 0
Received 3 Likes on 2 Posts
Default Pre-start cranking noise?

During my MS3X setup process, I've been cranking the engine to calibrate sensors. Last night during a 10sec cranking, about 5 sec into it, there was a change in the noise from the engine - rattling sound, with faint tones from the flywheel in the background. It might be the same time my oil pressure gauge pegged at 5? It happened again the next time I cranked - same pattern. At first I thought it was the starter making rough noise, but my worries got to me later and wondering if this was lifter/valve noise as oil pressure came up? That got me even more worried - what if I have the cams 180deg off? My only assurance that I installed the timing belt correctly 3 years ago is my details oriented thinking back then.
I can put the #1 cylinder at TDC (no plugs installed), but how do I know the valves are closed on #1 at this time? Put a plug in #1 and see if the compression stroke happens as the cam gear approaches the mark on the housing? This is a 1980 4.7L Euro S motor, with Castrox GTX 20-50 oil.
Old 06-05-2015, 11:39 AM
  #2  
Ducman82
 
Ducman82's Avatar
 
Join Date: Nov 2009
Location: Marysville WA
Posts: 6,983
Received 18 Likes on 11 Posts
Default

are you spinning it with the plugs out? spins faster and i got some good data logs on the trigger pulses that way.

i always worries about oil pressure with all that "dry" cranking. i ended up taking the timing belt off and spinning the oil pump with a drill and it worked like a champ. are the oil pressure sender wires on the right posts? i know that can cause the gauge to be dumb.

without firing the engine you will get some change in pitch and engine load when the pump starts pulling and pressurizing the oil.....
Old 06-05-2015, 12:04 PM
  #3  
BigAl1
Thread Starter
 
BigAl1's Avatar
 
Join Date: Jul 2010
Location: SW Ontario, Canada
Posts: 692
Likes: 0
Received 3 Likes on 2 Posts
Default

Yep, plugs out. I have to check the oil pressure sender connections, but supposedly it is just a variable resistor, so should not matter connection order. I'm going to try a pressure tester tonight - to verify I have both valves closed at #1 TDC. The engine speed would change very slightly when the extra noise started - hopefully it is just the oil pump pressuring the system.
Old 06-05-2015, 12:07 PM
  #4  
Ducman82
 
Ducman82's Avatar
 
Join Date: Nov 2009
Location: Marysville WA
Posts: 6,983
Received 18 Likes on 11 Posts
Default Pre-start cranking noise?

Stock sender has two wires. One for warning light and another for the gauge. I know when switched the oil pressure always reads max... Basically on/off
Old 06-05-2015, 12:11 PM
  #5  
BigAl1
Thread Starter
 
BigAl1's Avatar
 
Join Date: Jul 2010
Location: SW Ontario, Canada
Posts: 692
Likes: 0
Received 3 Likes on 2 Posts
Default

Thanks Jake - that sounds like my gauge problem - will look at that next chance I'm at the car. I think my wires were trashed when I got it, and had to rewire that stuff anyway, so easy for me to have them backwards.
Old 06-05-2015, 10:58 PM
  #6  
BigAl1
Thread Starter
 
BigAl1's Avatar
 
Join Date: Jul 2010
Location: SW Ontario, Canada
Posts: 692
Likes: 0
Received 3 Likes on 2 Posts
Default

All is well on the car - no rattling noise anymore. It could have been my lifters pumping up?



Quick Reply: Pre-start cranking noise?



All times are GMT -3. The time now is 01:28 AM.