Rebuilding injectors?

[JeepSJ]

I know I have a bed injector. The only local shop I could find to do rebuilds (and that uses Bosch nozzles) wants $40 each, and if I want them to match the pop pressures they consider that to be "blueprinting" and want an extra $10 each. I know I can go to one of our vendors and get a set for less than that.

But, what about rebuilding them myself? They just unscrew, change nozzle and spring, then shim to get the pop pressure that I want? I'm asking because I stumbled onto a set of brandnewstillinthebox Bosch nozzles for about $50 for the set of 8. Someone had posted a source for the springs and shims, and the plans for the home-built pop-tester.

Am I totally missing something here?

[DmaxMaverick]

That's about it. With new nozzles and a tester, you only have to worry about excessive internal bypass or actual physical damage (cracked body, etc.), which isn't usually an issue. It's worth a shot, IMO. Your end result may be better than any reman you can get.

[JeepSJ]

Thanks for the response. That brings up the next question -

Would excessive bypass be obvious from looking at what comes out of the return lines? Such as, if I looked at what was coming out of the return lines on all my injectors and they are all fairly even, then I'm probably OK, but if one or two have a much higher return flow then I know that those are totally shot?

[DmaxMaverick]

It will be obvious. Some bypass leakage is normal. If you are using a hand pump to test it and it is bypassing excessively, you won't be able to reach pop pressure. If you pump by hand, it pops, and dribbles out the return, it's OK. It should dribble a little, due to the pressure build against the spring, but it isn't always noticeable. The return "report" will indicate the general health of the injectors as a whole. They should all be about the same. It can squirt out the return after the pop, but only a dribble before. Doing it yourself, you can set the pressure a bit higher (50-100 PSI) with a 4911 pump. This will offer a more crisp combustion. Idle may be a little louder, though. It can decrease EGT's and help economy. Over a 200 PSI increase gets into "marine" specs.

[cakeordeath?]

What is the main advantage of putting a marine grade injector in a truck engine?

[DmaxMaverick]

What is the main advantage of putting a marine grade injector in a truck engine?

None in a "truck" engine, IMO. If you have a high performance need (competition), and the rest of the engine/drivetrain components are of the same level, it may serve to optimize power. Otherwise, no advantage. Driveability, idle and throttle transition qualities will suffer. A true "marine" application is a completely different environment for the engine. Primarily, the cooling systems are very different. When you have a whole lake/ocean to keep the engine cool, many common on-road conditions don't exist. And, a marine engine is most often operated at constant acceleration and cruising power levels. A truck engine uses the entire power range, from starting out to cruising, ascending grades, city traffic, passing, extended idle periods, etc. During most competition runs, the engine is operated (or attempted to) at or near the power peak during the run (drag racing or sled pulling). Also, idle quality, throttle transition and noise is generally dismissed as an exchange for performance in the power range. Additionally, drag racing and sled pulling is a very short event, compared to over the road towing and driving, in that the cooling system has very little required of it. This is why top fuel dragsters don't even have a cooling system, in the traditional sense (the high volume fuel is the cooling system). They may be able to go 300 MPH in a few seconds, but would melt down less than a 1/4 mile into a grade with a trailer in tow. Installing a big cam and straight cut timing gears in your 68 Camero has an appeal on the drag strip or car shows, but makes the car impractical (and many times, impossible) for daily driving.

[Robyn]

I have been into a couple sets and the most prominent issue other than the nozzles being worn out was a lot of carbon formation that had stuck the valve up to the point that it did not work well.

Doing a home rebuilt should not be too hard. Be sure to keep the parts matched to the injector it came from.

As long as the finished product will pop within the spec and "The spray pattern" is a fairly even cone of spray and not a pee stream.

If you can get these things working for you your set.
I aways spec my injectors to the top of the spec and "Even pressure"

Having the pressures all the same helps keep cylinder to cylinder timing the same.

This IMHO may have an effect on engine longevity as far as crank durability as well as the block.

Good luck and have fun.

Let us know how it all comes out.

Robyn

[JeepSJ]

I checked into the nozzles more and they are supposedly "marine" nozzles. He is getting me the part number so that I can verify the exact part and application. If they are the marine nozzle, do you see any problem with running the injector at truck specs (pop pressure)? I see a lot of rebuilt injectors being advertised with marine nozzles, but that does not necessarily mean it is a good thing.

[DmaxMaverick]

Most advertised "marine" injectors for trucks are not really marine. Two things make a true marine injector. Greater flow nozzle, and higher pop pressure. They go together, and one by itself is counter productive. If what you have is a true marine nozzle, and you don't increase the flow (pressure) to marine specs, or the spec range of the nozzle, it will not spray efficiently (more of a dribble than a spray/fog). The end result will be poor economy and power, more smoke, higher EGT's and possibly torched pistons. You need to verify the part number and spec with Bosch. At this point, I would not suggest using them unless you can match the pressure and flow volume with their spec. If you can verify they are instead "high performance" rather than true "marine", then they are probably OK. You really need to see the specs and compare them. Many vendors, especially those on Ebay, don't know what they are selling, but sell a boatload of them because they tell people what they want to hear. Ronniejoe or John8662 could probably inform you better than I.

[JeepSJ]

Most advertised "marine" injectors for trucks are not really marine. Two things make a true marine injector. Greater flow nozzle, and higher pop pressure. They go together, and one by itself is counter productive. If what you have is a true marine nozzle, and you don't increase the flow (pressure) to marine specs, or the spec range of the nozzle, it will not spray efficiently (more of a dribble than a spray/fog). The end result will be poor economy and power, more smoke, higher EGT's and possibly torched pistons. You need to verify the part number and spec with Bosch. At this point, I would not suggest using them unless you can match the pressure and flow volume with their spec. If you can verify they are instead "high performance" rather than true "marine", then they are probably OK. You really need to see the specs and compare them. Many vendors, especially those on Ebay, don't know what they are selling, but sell a boatload of them because they tell people what they want to hear. Ronniejoe or John8662 could probably inform you better than I.

I'll post up the part number as soon as I get it.

[dieseldummy]

I'd say go for it. There are alot of bosch knockoffs out there, but until you get them in your hands you can't know if they are good or not. I installed a set of "marine" nozzles at oem pop pressure (1800) and they are working great. They make a good mist when they pop and I've had not trouble from that aspect of things. It's alot cheaper to do it yourself and then you have the satisfaction of knowing exactly what's in your engine.

[JeepSJ]

Update - the price is $100/set, not the $50 that I originally heard.

He said that he can get the 0SD304(std) or the 0SD311(marine) nozzles.

In my search, I found this interesting test over on one of the other sites -



Stock tip # 304
Marine tip # 311
-----------------------------------------------------------------
Stand set to 70 cc fixed using test calibration nozzles
------------------------------------------------------------
3,000 rpm
________
311
130 bar 69 cc
142 bar 67 cc
146 bar 65 cc

304
142 bar 64.5 cc

1,600 rpm
__________
311
130 bar 41 cc
142 bar 51 cc
146 bar 46.5 cc

304
142 bar 49 cc

Conclusion: Marine injectors basically put out the same amount of fuel unless you drop the popping pressure to stock specs.

Marine injector output drops dramatically at low speed especially if you drop the pressure real low. Pressure plays a critical role with different combinations.



So it looks like the difference between the standard and the marine nozzle isn't much.

It also looks like Bosch rates the flow of the 304 nozzle at 142bar, which by my calcs is about 2080psi, and the 311 at 150bar which is 2200. I wish the tester would have tested the 311 at 150 bar as it looks like the output of those is dropping as the pressure is increased (which I would expect). Interesting that at the non-marine pressure the 311 does have a slightly higher output than the 304.

But based on what I am seeing, I'm thinking the 304 nozzles and get all my injectors popping as close as possible to each other and call it good. Since the 304 is rated at 142bar, I'm thinking that is where I will set my pop pressure.

[rhsub]

A WORD OF CAUTION
when testing injectors DO NOT spray onto your skin, fuel can enter your skin and cause blood poisioning
Where did you find this tester??? wouldn't mind having one too
Thanks
Ron

[DmaxMaverick]

Update - the price is $100/set, not the $50 that I originally heard.

He said that he can get the 0SD304(std) or the 0SD311(marine) nozzles.

In my search, I found this interesting test over on one of the other sites -



So it looks like the difference between the standard and the marine nozzle isn't much.

It also looks like Bosch rates the flow of the 304 nozzle at 142bar, which by my calcs is about 2080psi, and the 311 at 150bar which is 2200. I wish the tester would have tested the 311 at 150 bar as it looks like the output of those is dropping as the pressure is increased (which I would expect). Interesting that at the non-marine pressure the 311 does have a slightly higher output than the 304.

But based on what I am seeing, I'm thinking the 304 nozzles and get all my injectors popping as close as possible to each other and call it good. Since the 304 is rated at 142bar, I'm thinking that is where I will set my pop pressure.
I'm still skeptical. That test is not in any way accurate.

Fuel volume is determined at the pump. Pressure is determined at the injector. If the test stand was in fact set a 70cc, then all results should be 70cc. The drop in volume as the pressures are increased indicates a pump that isn't constant displacement. The "RPM" is irrelevant. RPM is not indicative of fuel delivery.

That test only confirms the "marine" nozzles have a larger hole than stock. We already knew that.

I still think you should verify exactly what you have, or will have, before using them.

Good advice about not spraying on your skin. 500 PSI is more than enough to inject fluids into your flesh. Not much more than that can sever digits, under the right (wrong) conditions.