Author Topic: Injector problems (Read 5969 times)

silvertdi · « **on:** November 12, 2007, 07:44:34 pm »

I've noticed my fuel mileage dropping and the number 4 injector a bit oily and getting dirty. I figured it was the fuel line nut and checked it. It wasn't. Fired it up and got a bright light out to look for the leak. I found it. The injector is leaking in the center where the upper part connects to the lower part. My question is this...can I replace just one, or should I do all 4 as a set? Also, can I get more power by putting an injector from a different model in it? It's an 81 N/A with no mods to date. Any good vendors? Parts place wants $50 for Bosch rebuilt with new Bosch nozzles. Thanks.

jtanguay · « **Reply #1 on:** November 12, 2007, 09:05:05 pm »

are you sure that is the area that is leaking? the injector return hoses are most likely culprits, and can leak fuel down giving you a false visual. pull out the compressor air nozzle to spray away the fuel while its running. then you will get a better idea.

silvertdi · « **Reply #2 on:** November 13, 2007, 03:52:08 am »

I've replaced the return line with OEM return line and I've sprayed the area off with contact cleaner a few times. You can actually see the bubbling around the seam where the two halves of the injector meet. They're very tiny bubbles at idle and you can watch the gap at the seam well up with fuel.

silvertdi · « **Reply #3 on:** November 13, 2007, 02:57:30 pm »

Anyone with upgrade info on injectors for an 81 NA. I'd like to get injectors that can be used in a TD as that is the direction my build will take me, but I don't want to install a TD injector on an NA if its not appropriate. Any input?

Vincent Waldon · « **Reply #4 on:** November 13, 2007, 04:23:17 pm »

Leaking at the seam is not uncommon because there's no gasket internally... it's metal-to-metal.

You can try pulling the injector and re-torquing the body halves, or take it apart and re-lap the surfaces, or get new ones... how many miles on your current set ??

silvertdi · « **Reply #5 on:** November 13, 2007, 05:27:33 pm »

They're original with 103,000 miles.

Vincent Waldon · « **Reply #6 on:** November 13, 2007, 06:26:01 pm »

Quote from: "silvertdi"

They're original with 103,000 miles.

Go for new ones... 100K miles is probably enough from an economy and performance perspective.

rallydiesel · « **Reply #7 on:** November 13, 2007, 06:36:00 pm »

I was talking to a Bosch tech not too long ago and he said that this is often due to what he called the intermediate plates getting worn out. They are the cone-shaped spacers that the spring sits on. Mine don't leak after having these replaced when I had my injectors calibrated.

silvertdi · « **Reply #8 on:** November 13, 2007, 08:11:43 pm »

Thanks for the help. Looks like I'll be ordering a set. Is there a bigger injector I can run for added performance?

silvertdi · « **Reply #9 on:** November 16, 2007, 08:53:39 pm »

Put some rebuilt injectors in today. Runs pretty good. Sounds a little more clackity but I like the sound. It doesn't knock, just more big rig like. They don't appear to be leaking and it feels smoother. Let's hope my cold weather starts are better (It was starting to get tough and we're only in the 30s).

jtanguay · « **Reply #10 on:** November 17, 2007, 12:21:50 pm »

Quote from: "silvertdi"

Put some rebuilt injectors in today. Runs pretty good. Sounds a little more clackity but I like the sound. It doesn't knock, just more big rig like. They don't appear to be leaking and it feels smoother. Let's hope my cold weather starts are better (It was starting to get tough and we're only in the 30s).

does your idle increase with the cold start lever pulled out? check your pump if you have the capability for it. i've brought mine up to around 1100 rpm's for cold start and it starts up real good

silvertdi · « **Reply #11 on:** November 17, 2007, 12:24:41 pm »

The idle does not increase when I pull the cold start lever out. I may turn my idle screw up a bit too. One thing the injectors did do is stop the cold idle vibration problems I was having. Before, the dash would shake, doors would shake, etc. until it warmed up a bit.

Quantum TD · « **Reply #12 on:** November 17, 2007, 03:43:17 pm »

Quote from: "jtanguay"

does your idle increase with the cold start lever pulled out? check your pump if you have the capability for it. i've brought mine up to around 1100 rpm's for cold start and it starts up real good

On the older MKI cars, the cold start lever really only increases the engine idle if you have the injection pump drastically retarded (i.e. below about .95 timing). The idle-up style cold start lever only appeared on the later 1987-up cars. You can see the extra parts that connect to the accelerator lever.

I struggled with this concept myself. I couldn't figure out why my 1984 Rabbit 1.6NA would not idle up on cold starts with the lever out, when I had it set to 1.00 pump timing. While working on an ECODiesel, I saw the second lever for the accelerator. Later while working on a 1981 Caddy diesel, I set the injection pump timing to 1.00mm with the cold-start lever out. I forgot I had done that, and when the car was warmed up with the lever in, it idled low and like crap. I finally figured out my goof, and reset tht pump timing to 1.00mm with the lever pushed in. Afterwards, the idle would not change at all when the lever was out, just like my 1984