Hello Guys,
2001 f-350 7.3

I have been getting a check engine light for some time , it tells me the glow plug are bad , it's the # 4 / #6 / latley the #8 / I changed out the first two but the light came back on in a short time ,it jumps around , I changed the harness under the valve cover, no change , I changed the valve cover gasketbecause the plug was not locking well , cleared the signals and the # 8 poped up as bad again . The dealer recomends changing the glow plug relay , around $230.00 , has anybody experianced this problem ? I would appreciate any feedback before buying the relay. Thanks

 

Is it always the same cylinder numbers that fail? Did it have any prior heat damage to the UVC gasket, or harness/s under the covers? Did you check the connectivity of the engine side harness connector terminals?any evidence of excessive heat there?