300ZX (Z31) Performance / Technical Discussions related to Turbo charging, Supercharging, Engine, ECU, exhaust, and etc. performance enhancements and Techical related.

Hard Start When Cold

Old 02-08-2018, 06:55 PM
  #1  
Registered User
Thread Starter
 
Join Date: Feb 2018
Posts: 3
Question Hard Start When Cold

So, I have an 85 Z31 N/A that has a difficult time starting when cold. If I let the fuel pump prime a few times before starting or use starting fluid she will fire right up. She will also stay running and restart without any issue for the rest of the day. I have installed a new fuel pump, and FPR, checked the fuel pressure, spark, vacuum, and the ECU is clear. Everything seems to check out as per the FSM. The only strange thing I see is the FSM has 2 different configurations for the FPR fuel hose routing, one for turbo and the other for N/A. I have an N/A that appears to be routed like a turbo. Any input would be greatly appreciated. Thanks
deonw1 is offline  
Old 02-14-2018, 07:01 AM
  #2  
The Good Twin
 
NismoPick's Avatar
 
Join Date: Aug 2005
Location: Wild Wild West, UTAH!
Posts: 20,616
Welcome to ZDriver! So when you check fuel pressure, what's it at? Did you do a leak down test?
NismoPick is offline  
Old 02-15-2018, 02:02 AM
  #3  
Registered User
 
Join Date: Feb 2017
Posts: 3
Originally Posted by deonw1 View Post
So, I have an 85 Z31 N/A that has a difficult time starting when cold. If I let the fuel pump prime a few times before starting or use starting fluid she will fire right up. She will also stay running and restart without any issue for the rest of the day. I have installed a new fuel pump, and FPR, checked the fuel pressure, spark, vacuum, and the ECU is clear. Everything seems to check out as per the FSM. The only strange thing I see is the FSM has 2 different configurations for the FPR fuel hose routing, one for turbo and the other for N/A. I have an N/A that appears to be routed like a turbo. Any input would be greatly appreciated. Thanks
Hey everyone, and to op, sorry this is diff from what u guys are talking about but have u changed the thermostat or is it even still there?
87moonglow is offline  
Old 02-15-2018, 05:54 AM
  #4  
Registered User
Thread Starter
 
Join Date: Feb 2018
Posts: 3
Originally Posted by NismoPick View Post
Welcome to ZDriver! So when you check fuel pressure, what's it at? Did you do a leak down test?
When it first primes the pressure is at 34 psi and after starting ~25 - 26 psi. And yes, I did a leak down test, but I forgot the exact time frame it took for the pressure to bleed down, but it took over an hour. I may have to do the bleed down test again to get you a more accurate answer. I read on post that someone had a similar issue and removed the fuel return line and it help. Possibly some blockage in the return line? Thanks again for your help.
deonw1 is offline  
Old 02-15-2018, 05:58 AM
  #5  
Registered User
Thread Starter
 
Join Date: Feb 2018
Posts: 3
Originally Posted by 87moonglow View Post
Hey everyone, and to op, sorry this is diff from what u guys are talking about but have u changed the thermostat or is it even still there?
No , I haven't changed the thermostat, yes it is still there and working as far as I can tell. So what's your theory?
deonw1 is offline  
Old 02-16-2018, 01:45 AM
  #6  
Registered User
 
Join Date: Feb 2017
Posts: 3
Originally Posted by deonw1 View Post
No , I haven't changed the thermostat, yes it is still there and working as far as I can tell. So what's your theory?
It would generally take longer for the car to warm up, and now that I rethink that, it would only effect the coldstarts after the engine has been running, Im not positive though about the latter tho. Another brainstorm would be the MAF/ throttle body being dirty (maybe IDK) iv cleaned mine before and it helped my idle/coldstarts slightly
87moonglow is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
bongpogi
280ZX Performance / Technical
3
08-19-2015 11:15 AM
Treacy
300ZX (Z31) Performance / Technical
5
11-14-2013 11:23 AM
HybridS130
280ZX Performance / Technical
19
12-05-2005 04:59 PM
Wolfe
300ZX (Z31) Forums
2
12-24-2001 09:55 PM


Thread Tools
Search this Thread
Quick Reply: Hard Start When Cold


Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.