Pop Testing Injectors
 

I am having some injector trouble on my '81 300D(non-turbo) and I am trying to decide whether I should buy new injectors or used injectors that have been pop tested.

If an injector pop tests within the acceptable range, does this mean the nozzle is good?

Can an injector have a good pop test with a bad nozzle?

Will a good pop test ensure proper spray pattern?

If I buy the used injectors that have been pop tested I may replace the nozzles as well.

Anybody have any advice/ideas to offer?

What is the price difference?

Bad nozzles can be in a otherwise good injector that pops at the correct pressure. If possible watch the injector in question and see that it does not "pee" but instead sprays. Nozzles are a wear item- at say 100-150K.

I just found some Monark rebuilt injectors for $295 for the set of five including heat shields. $35 core charge will be refunded.

I found a set of five injectors on Ebay and the guy agreed to sell them to me for $75. He pop tested them all and they are within range. I am waiting to hear back from him to find out how many miles are on them and what the spray pattern looks like.

I have found a set of Monark nozzles for about $120 shipping included. I don't have a tester though so I would be going blind if I were to just replace the nozzles without testing them.

I read DieselGiant's writeup on rebuilding them yourself and he never mentions pop testing them when he's through. Do you think this is an oversight or you don't need to test them?

Pop testing tests the pressure with the nozzles that are installed. When you change nozzles the previous pop testing results no longer apply. If you are going to install new nozzles there is no reason to buy injectors that have been previously tested. If the injectors you are looking at have been pop tested and have a good spray pattern go ahead and run them without changing the nozzles.

Don't buy anything just yet.
 

Pm sent.

re: dont buy buy anything yet
 

hey Sean, Im in the same boat, would you pm also...

I'm dittoing what MTUpower is saying...Personal preference. Not always.Yes it can.

No, pop test refers to the minimum pressure the nozzle first opens.

If you decide to do it yourself, you MUST be absolutely as clean as possible -- along the lines of operating room or NASA clean room.

Perhaps one other way is to send your injectors to Sean if he will test them and rebuild hem if necessary. If you buy somebody's injectors, you are at their mercy as far as whether it pops and sprays well.

If you get used injectors be sure they have been checked for proper pop pressure AND spray pattern. If you opt for rebuilt injectors I rebuild injectors for members here for much less than the $295 you were quoted.

I bought some used injectors with only 70,000 miles for a $100.last Year.I can't wait to buy rebuilts with Monark nozzles.Don't buy used injectors.People lie like Dogs.

pop testing - necessary for new injectors?
 

I purchased new nozzles (bosio). Is there any need to pop test these before install, or can I just put them in?

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Thanks!
Joe.
82 300D turbo
169K mi.

Yes. Otherwise how will you know hat shims to put in to set the pressure?

He failed to do the job properly. I replaced my nozzles and one of my injector's pop pressure was way off. You'll never know unless you pop test them. Yeah, it might be close enough and get you by; but if you want it done right, you need to pop test them.

Scott

While you are making sure the injectors are set to right pressure and have good spray pattern... is a good time to make sure the precombustion chamber pintle and holes are in good shape... otherwise that careful work will be wasted.