LQ4 hard start after warm??
Thread Starter
Teching In
Joined: Jun 2017
Posts: 38
Likes: 4
LQ4 hard start after warm?? Hello,
The current problem I'm having with my LQ4 is hard starting or not starting after the engine has reached operating temp.
If I open the hood and let it cool off for 5 minutes it will start back up.
Current set up:
LQ4 engine with cam and heads.
walbro 255
C5 fuel pressure regulator
8.1 marine injectors
Dyno'd and tuned currently.
I thought it was possibly a vapor lock issue. So I upgraded the cooling system, insulated my fuel line and fuel rails. No change, still having the hard or no start after warm.
Symptoms began soon after new 8.1 marine injectors. Could the injectors be leaking and flooding the engine?
The current problem I'm having with my LQ4 is hard starting or not starting after the engine has reached operating temp.
If I open the hood and let it cool off for 5 minutes it will start back up.
Current set up:
LQ4 engine with cam and heads.
walbro 255
C5 fuel pressure regulator
8.1 marine injectors
Dyno'd and tuned currently.
I thought it was possibly a vapor lock issue. So I upgraded the cooling system, insulated my fuel line and fuel rails. No change, still having the hard or no start after warm.
Symptoms began soon after new 8.1 marine injectors. Could the injectors be leaking and flooding the engine?
TECH Senior Member
Joined: Jun 2016
Posts: 22,295
Likes: 3,619
From: Central Cal.
You might have a heat-sensitive bad electrical connection in an ignition or injection circuit. Five minutes cool-down is not much for an engine, but enough for electrical components to cool sufficiently to re-establish a connection.
Thread Starter
Teching In
Joined: Jun 2017
Posts: 38
Likes: 4
That is very interesting!! Now that you mention it, when it is cranking over it is spinning like there is no spark. The wiring harness is one I got from Speartech.
Do you know if there is a way I can test the connectors?
This is my daily driver and causes a lot of embarrassing moments when it doesn't start back up. For ex: ordering food at the drive-thru. I had to push it out of line because I turned it off to order! Hahaha
Do you know if there is a way I can test the connectors?
This is my daily driver and causes a lot of embarrassing moments when it doesn't start back up. For ex: ordering food at the drive-thru. I had to push it out of line because I turned it off to order! Hahaha
I have the exact same issue with the LQ4 in my work truck, 2006 Isuzu NPR. When warmed up after driving it will be hard to start, let sit for 5-10 minutes it fires right up. I have tried new plugs, plug wires, and coolant temp sensor with same issue. I havnt had a chance to look to much into it.
Have you tried checking the spark once its warmed up to see if it does actually have spark?
Have you tried checking the spark once its warmed up to see if it does actually have spark?
Thread Starter
Teching In
Joined: Jun 2017
Posts: 38
Likes: 4
No I haven't checked spark yet when it happens. I think you might be right. I am running some cheap autozone wires. I'll pick up some OEM gm wires tomorrow and see if that fixes it. Heat related electrical problem... it's a first for me! Thank you guys!!! I'll let you know tomorrow if it fixes it.
