So, I had my passenger side head replaced 3 years ago & just recently noticed hard start when below 50 degreees. I replaced GPR & it is working fine but when I test the glow plugs with a test light, All 4 on the passenger side are bad. All 4 are good on drivers side. Is there a reason why this could be? Truck has 90000 miles on it.

 

Have they been working for the last 3 years …? If not then I guessing a wire is off or missing. How do the pins look?

 

Not sure. Only put about 6000 miles a years on it. Just noticed this.

 

Pins look good

Going to pull the valve cover now

 

What does your multimeter say the voltage is when the GPR is activated?

 

Do you know what brand glow plugs were installed in the new head? Can you ohm test the glow plugs?

 

Duplicate thread merged with this one.

Stewart