Is this injectors?

[sctrailrider]

I am in Pauline,SC, about 80-90 miles up I-26 west from you, I have a new Clones timing set you can have really cheap if you want to try it. I think you are bypassing the one place I would look, the IP, if you had bad stuff that made it into the pump it would cause bad things inside it.

I also agree that you need to try and narrow things down and not just throw parts at it hopping for the fix.. Pull the codes, if you aren't sure how, say so and we will tell you how to do it.

A surging can mean several different things, you need to first see if there are any codes, if not, might try a new good PMD, not the cheap ones.

If you get stranded up this way, I might can help ya.

[65-f100]

The p0004 code is the only code it had other than a transmission circuit code that it has had for years. I do have a scanner and will check codes again when we get home.

Based on the fuel contamination I've worked my way from the back forward trying to think logically. I'm really trying not just to throw parts at it. The tank was full of material hence I replaced it and the fuel sending unit (Gauge had been bouncing for a while anyway). The next step was blowing out the lines and replacing the fuel filter unit. The filter unit has been seeping a little fuel anyway and also had trash in it, so I just replaced the whole thing. Both sending unit and filter housing are new Delco units. After testing the lift pump and seeing the pressure drop to 0 under load - it was replaced. Thiinking this was still fuel related based on the symptoms - the next step in my mind was injectors.

The PMD was replaced with a known good unit that was pulled off my last new IP (I have the heath remote mounted PMD currently).

I asked about the IP on my fuel contamination post, but the consensus was that it should not have been affected. I did take the injectors I pulled out apart and there was no noticaeble trash in any of them. Now I know that if could still be in the pump and never made it to the injectors, but how do I verify that?

Are there other ways for me to test the IP other than the hold it steady at 2000 rpm test?

The symptom really occurs under steady throttle (Highway driving). It really does not kick and buck too much in around town driving when you're on and off the throttle. I was thinking that slack in the timing chain would cause the timing to jump around under steay throttle and may not be as noticeable in on and off throttle since the slack probably tightens under load. Is this reasonable?

Did add an extra dose of stanadyne grey additive to my last tank of fuel just for good measure.

Trailrider - thanks for the offer on the chain set - may take you up on that. I'll let you know.

Next step?

[greatwhite]

I can't remember if this was suggested already and its going to sound cliche, but have you checked and cleaned the ground points yet?

[JohnC]

Try removing (bypassing) the optical sensor filter. It has been suspected in this sort of behavior. Also, when was the last time the fuel filter was changed? Where are you measuring pressure, before or after the filter?

[Kennedy]

If you had fuel/tank contamination then the fuel injection system is the place to start. If changing relatively low miles injectors helped that leaves one key component. Just be good and darn sure that your fuel supply is good and clean before you replace the pump.

[bshull]

Just a very blind shot in the dark, did you check the fuel strainer under the fuel inlet on the IP? With known fuel contamination you have mentioned replacing filters ect, what is the condition of the inlet screen?

Like I said, shot in the dark. Good Luck!

Brian

[65-f100]

OK - latest update.

I drove the truck home approx 4 hours. Still driving much better than it was prior to the injector replacement, but still surging pretty consistently. Not bucking like it was before.

It really does feel fuel or timing related. I have to give it a lot more throttle than I normally do to get it up to speed.

Kennedy - what is the best way to test the fuel? I've burned through almost a full tank with extra stanadyne grey added. Just refueled on the way home at a Pilot truck stop so I'll keep driving it to see if it changes behavior.

bshull - I was not aware of an inlet filter on the IP. Is it a screen type filter? Is it where the rubber line attaches from the filter housing? Certainly worth a try.

I still plan on replacing the timing chain based on the miles - opinions on chain vs. gears?

Thanks!

[bshull]

The ip inlet filter is below where the rubber fuel line enters the IP, unscrew the compression nipple and remove the fitting that the nipple screwed into. You might be chasing a ghost but to check it cost nothing but a little air in the system.

I have timing gears, some swear by them, some swear at them. The question is how much longer do you plan on running that engine? A good timing chain is cheaper and will probably outlast the engine.

Good luck

Brian

[65-f100]

bshuill - I will check that tomorrow - it very well could be that if some trash got through. Certainly worth the time to check it. How nice it would be if you are correct!

We're planning on keeping it for several more years. On the gears - not as much worried about the longevity as the chain on there now is a little over 300K. I've ready many posts from other using them that they have experienced better drivability (crisper throttle) a little more pwer and maybe a slight bump in mpg. What has your experience been?

Thanks

[bshull]

It is hard for me to tell, I put in the P-400 engine, att turbo, and heath tune at the same time as the gears so I do not have a direct reference.

I pull 18 mpg pushing 75 mph on the highway and for a burb that has 3.42 gears it performs very well.


Brian

[sctrailrider]

I think you might find the strainer plugged up, it is the only thing you haven't checked yet.

As for the gear or chain ---- with 300k on the motor, I would go with a new chain set if it were me, I am going to a gear drive in my build just because it will be a new motor, it mine had that many miles and I wanted to freshen things up, the money for the gears would be better spent on a better turbo than the GM junk.... just my thoughts...and you should consider a new balancer if you haven't replaced it yet...

[65-f100]

Latest update:

Inlet filter certainly had trash in it. Bshull I thought you had nailed. It had enough in it that I thought it was going to solve my problem. If only I were so lucky. I cleaned it out good. Took both little screens off and blasted them with brake cleaner and air. Opened the little spring loader valve on the end as well. It was very clean when I reinstalled it.

Truck has noticeable more power on the top end once it hits about 2500 but its still struggling somewhat to get there. I'm narrowing down to the IP which I've been trying to avoid. Thinking some trash still got through and may have damaged it? It's still starting hard and stilll surges going down the road. If I rev it in neutral and hold it around 1800-2000 - you can actually hear and feel it missing. It will hold the rpm steady but it has the occasional little surge by itself. Not running away like one of failing ones in the past. Not exactly sure on the internals of the pump, but it really feels like I have 1 or 2 cylinders missing. Does the IP have separate internal valves for each cylinder?

Would a cylinder balance test help me determine if it's the IP?

Thanks for the continued help. Every little thing I've done is making it better. I'll still probably go ahead and put a timing chain set on since it's overdue and would give me some peace of mind. It would also eliminate that as a factor too.

[greatwhite]

Your 1800-2000 rpm "surge" is not a positive sign of ip health. As in; not good.

I would be interested in some real time data from a proper scanner to see what it's doing....

[bshull]

GreatWhite is right, things are pointing at the IP. It would be nice to see some data from a good scanner.

To recap your problems, you have a surging bucking problem at steady throttle. Bottom end power feels weak.

Things done, new injectors, different PMD, fuel supply system fully cleaned, fuel system air tight.

If it were me, I would replace the IP. Still not 100% sure but with everything done it really sounds like IP. I would want scanner data to back it up before spending a grand tho.

Let us know where you are going to proceed,

Good luck

Brian