New engine... Running odd.

[KevinSonOfDad]

I just finished putting in a brand new rebuilt 4.0 in my truck this weekend. It runs and drives but seems underpowered and shakes a lot at idle. I auspect injectors since im using the ones fROM the junkyard motor I rebuilt instead lf my previous ones.

What sympotms have yall had with bad injectors?

 

[superj]

pull them and run some cleaner through them. or at least spray them into a jar and make sure they are spraying properly and putting out a similar amount

 

[rubydist]

Bad injectors will cause anything from a slight unevenness in how it runs all the way to it won't run at all, depending on how many injectors are sticky and how badly they are clogged. Your symptoms could easily be dirty injectors.

 

[dvdswan]

Why not throw in the previous injectors you have?

 

[Shran]

I sent mine off to be cleaned by Mr. Injector - I did have sort of an uneven idle before, I only really noticed because the transmission shifter would shake. There is a noticeable difference now, idle is much smoother. No difference in power while driving.

The only reason I sent them off was because one got stuck open and it would run horribly rich and smoked a lot. I got a flow chart back with them that indicated a couple of the others were not working quite right either.

In my experience they are probably the last thing I would look at, it's totally possible to have one or more malfunctioning, but far more likely that it's something else.

 

[KevinSonOfDad]

Why not throw in the previous injectors you have?

Thats the plan today. Since so many variables are different from the last engine im trying to narrow down the possibilities

 

[KevinSonOfDad]

Bad injectors will cause anything from a slight unevenness in how it runs all the way to it won't run at all, depending on how many injectors are sticky and how badly they are clogged. Your symptoms could easily be dirty injectors.

Thats my thought. Also because they came from a engine in unknown condition. I plan to swap back to my old ones as a test since my old engine ran good with them and they all test good

 

[KevinSonOfDad]

pull them and run some cleaner through them. or at least spray them into a jar and make sure they are spraying properly and putting out a similar amount

How exactly would i spray them into a jar?

 

[superj]

just pop it out and point the injector into a mason jar. crank the truck over and measure the amount for a certain amount of cranks. you can also power it up with a 9v battery and run some cleaner through it yourself with a spray bottle or a bottle you can add pressure to in order to push the cleaner through when you apply 9v to the power side.

the bmw guys did this alot

 

[KevinSonOfDad]

just pop it out and point the injector into a mason jar. crank the truck over and measure the amount for a certain amount of cranks. you can also power it up with a 9v battery and run some cleaner through it yourself with a spray bottle or a bottle you can add pressure to in order to push the cleaner through when you apply 9v to the power side.

the bmw guys did this alot

Just seems difficult due to the design of the 4.0 fuel rail.

 

[KevinSonOfDad]

UPDATE: after running it for longer I noticed discoloration on all but 2 of the headers. Turns out indeed cylinders 5 and 6 are dead. Got spark and after swapping around injectors to confirm indeed i have 2 bad injectors. Will swap them out today and update with how it went.

 

[KevinSonOfDad]

TLDR: look for bolded underlined questions

Ok so i swapped in my old set. It ran slightly better and 5 and 6 are now firing but now 1 and 2 are dead or partaily dead. Truck is parked till this is fixed as to not damage the brand new engine.

Since swapping to an old set changed the dead cylinders and swapping between cylinders does i know the problem isnt in wiring. But i am curious if my old set had 2 dead injectors just like the new one since the truck ran ok on the old set.

Part of me suspects the fuel pressure regulator now also its cheaper to fix than 400 bucks of injectors.

What are the failure modes of the regulator? I unplugged its vaccum while running and the sound and speed of the engine didnt change(may not be a great test since its already only running on 4 cylinders.

what things should I test before getting new injectors?

 

[Shran]

I would send a set of 6 off to be cleaned and tested... it was only about $150 after shipping when I did it. Totally worth it. And it is not a crap shoot gamble like buying new ones is......... you know they will be tested and working.

I really doubt this is a regulator issue. Usually if that fails it is just the diaphragm inside that ruptures and engine vacuum pulls fuel out of it... bad gas mileage and hard starts when warm are the main symptoms.

 

[KevinSonOfDad]

I would send a set of 6 off to be cleaned and tested... it was only about $150 after shipping when I did it. Totally worth it. And it is not a crap shoot gamble like buying new ones is......... you know they will be tested and working.

I really doubt this is a regulator issue. Usually if that fails it is just the diaphragm inside that ruptures and engine vacuum pulls fuel out of it... bad gas mileage and hard starts when warm are the main symptoms.

Where did you send yours?

 

[Shran]

Where did you send yours?

Mr Injector

We service and restore gasoline fuel injectors and gasoline direct fuel injectors to like new performance.

www.mrinjector.us

Highly recommended and quick turnaround.