Hot=will not start
#1
Rennlist Member
Thread Starter
Hot=will not start
Vehicle starts and runs normal at operating temperatures.
If I try to start once hot, vehicle will not start until it cools.
Engine cranks but will not start.
I cleaned grounds, replaced LH with know operating one and still not good.
Anybody had this situation, any ideas what can be causing this issue?
If I try to start once hot, vehicle will not start until it cools.
Engine cranks but will not start.
I cleaned grounds, replaced LH with know operating one and still not good.
Anybody had this situation, any ideas what can be causing this issue?
#3
Inventor
Rennlist Member
Rennlist Member
Are the plugs wet after an attempted hot start?
Bad Temp2 sensor (worn in hot range)?
Bad Temp2 sensor (worn in hot range)?
#4
Rennlist Member
These are also symptoms of thrust bearing failure. What year is your car, and is it standard or auto?
#5
Rennlist Member
Thread Starter
[QUOTE=Speedtoys;17531325]How long does it have to cool?
Vapor lock?
Temp2 sensor
really bad leaking FPR/Damper diaphrams?[/QUOTE
The vehicle cools for approximately 15-20 minutes
Vapor lock?
Temp2 sensor
really bad leaking FPR/Damper diaphrams?[/QUOTE
The vehicle cools for approximately 15-20 minutes
#6
Rennlist Member
Thread Starter
#7
Rennlist Member
Thread Starter
Trending Topics
#8
Rennlist Member
Michael,
If you have a problem with the diaphragm on one of either the FPR or dampers when you switch off the engine the fuel rail will lose pressure quickly and with the heat soak present the fuel can vapourise inside the rail and then the car will not start until the thing cools off and the fuel condenses once more. Cranking the motor theoretically should reinstate the pressure but i suspect being at a high point in the system the vapour gets high point locked and does not wash out. Similar thing if an injector is leaking
If opening the bonnet sees the problem resolve itself "quicker" that might confirm the above.
i doubt it is a TBF issue but then you should know for a fact such is not happening and if that is not the case then you need to ensure you know for a fact that all is well.
If you have a problem with the diaphragm on one of either the FPR or dampers when you switch off the engine the fuel rail will lose pressure quickly and with the heat soak present the fuel can vapourise inside the rail and then the car will not start until the thing cools off and the fuel condenses once more. Cranking the motor theoretically should reinstate the pressure but i suspect being at a high point in the system the vapour gets high point locked and does not wash out. Similar thing if an injector is leaking
If opening the bonnet sees the problem resolve itself "quicker" that might confirm the above.
i doubt it is a TBF issue but then you should know for a fact such is not happening and if that is not the case then you need to ensure you know for a fact that all is well.
#10
Rennlist
Basic Site Sponsor
Basic Site Sponsor
TBF not very common in '85/'86 engines.
Dampers/regulator should be the first place to check....super common.
And even if the dampers aren't leaking, most of them no longer are able to move, due to the diaphragms getting rock hard. This causes severe pressure waves in the fuel rails...resulting in both lean and rich running conditions.
928 International sells my fantastic reproductions, if yours are leaking/old.
Dampers/regulator should be the first place to check....super common.
And even if the dampers aren't leaking, most of them no longer are able to move, due to the diaphragms getting rock hard. This causes severe pressure waves in the fuel rails...resulting in both lean and rich running conditions.
928 International sells my fantastic reproductions, if yours are leaking/old.
Last edited by GregBBRD; 07-04-2021 at 11:58 PM.
#11
Rennlist Member
Join Date: Nov 2011
Location: Adelaide, South Australia
Posts: 719
Likes: 0
Received 74 Likes
on
41 Posts
This exactly what happened to one of my 86 cars and it was a loose/broken wire on temp sensor 2.
This incorrectly tells the LH unit that the engine is cold [because it isn't getting the signal] and it richens the fuel mixture for cold start.
Re-soldered the connection and never had another issue.
This incorrectly tells the LH unit that the engine is cold [because it isn't getting the signal] and it richens the fuel mixture for cold start.
Re-soldered the connection and never had another issue.
The following users liked this post:
Speedtoys (07-05-2021)
#13
Rennlist Member
TBF not very common in '85/'86 engines.
Dampers/regulator should be the first place to check....super common.
And even if the dampers aren't leaking, most of them no longer are able to move, due to the diaphragms getting rock hard. This causes severe pressure waves in the fuel rails...resulting in both lean and rich running conditions.
928 International sells my fantastic reproductions, if yours are leaking/old.
Dampers/regulator should be the first place to check....super common.
And even if the dampers aren't leaking, most of them no longer are able to move, due to the diaphragms getting rock hard. This causes severe pressure waves in the fuel rails...resulting in both lean and rich running conditions.
928 International sells my fantastic reproductions, if yours are leaking/old.
This is what Greg's new HW looks like, installed.
Tucks nicely into the rear as well.
#14
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
I had a very hard to diagnose similar issue - would not restart and run after fully warming up but would start & run fine from cold.
After lots of work turned out to be the ISV that was sticking closed only after the engine had heated up - I was surprised it worked that way around. On the bench it had tested out fine - if not it would have been swapped out for diagnostic purposes sooner.
Alan
After lots of work turned out to be the ISV that was sticking closed only after the engine had heated up - I was surprised it worked that way around. On the bench it had tested out fine - if not it would have been swapped out for diagnostic purposes sooner.
Alan
#15
Advanced
Join Date: Aug 2010
Location: south shore,long island
Posts: 57
Received 0 Likes
on
0 Posts
Good morning Bimmermike. I once had the exact same issue with my 87 S4/ 5 speed. It was nothing more than a faulty fuel pump relay. Start with the simple stuff first. I got stuck more times than I care to remember. It hasn’t happened since I replaced it.