I would measure resistance on all the glow plugs first to determine which ones need replacement - use Dieselgiant's how-to on this subject. He does a good job explaining the troubleshooting procedure.

You may find that only the first or the last GP needs to be removed and replaced - if so, you probably won't need to pull the hard lines off for that. I fretted taking the hard lines off for a long time but eventually I had to take them off to measure compression on the engine and it really was not so bad.

IF you decide to take them off - make sure you apply plenty of time and patience - you don't want to cross-thread anything there as they may be under slight tension. You'll need to bleed the air out of them once you're done. Make sure you have a strong battery as you'll need to crank a while before it starts.

Good luck -
James

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K