After 300 mile roadtrip I got back home to slower speeds and a noidy off-idle rattle.

[nyoffroad]

Dependable, new glow plugs 3 months ago as a matter of maintenance. New fuel filter last month. Never used ether or other sprays. I was leaning towards rod knock, but want to DIY as much as I can before outsourcing the bottom end work. I have heard of bad fuel as a source of the knocking. If the fuel is contaminated, how can I tell?

Drock, I'll have a good look at the flexplate bolts, but I have some smoke that accompanies the noise; would that jibe with a cracked flexplate?

I one time filled up at a small mom n pop type station and ended up with a partial tank of gasoline, truck ran like crap and lost power and IIRC it smoked too. I'd run a tempory fuel line to a clean can of fuel and hope that the engine settles down and runs right. Good Luck!

 

[edpdx]

So, to update; I am reporting that the knocking has returned. I did not get thru more than half a tank since the knocking went away- now it's back.

I checked the flexplate- no cracks; the bolts to the torque converter are solid. I replaced the oil and filter; the fuel filter. No improvement. It still knocks off idle, and during load. The noise subsides at cruising speed. When I do have it under load to get up to traffic speed, it smokes light gray from both pipes.

I filled the tank to see if it would dilute any bad fuel, but I didn't have much hope because I emptied the fuel filter into a quart jar; there was no water or visible contaminants.

Today I just pulled all of the glow plugs to be sure the tips were intact, and not the cause of the rattling. All ok (3-4 months old).

Last on my check list is to pull the valve covers and look for a rod that's off it's rocker. After that I am out of home remedies to try. I'll have to assume rod knock and take it to a diesel shop.

Any other ideas you can send my way before I get out my checkbook would be greatly appreciated.

 

[edpdx]

What should the fuel pressure going in to the Injection Pump be at?

MY spin-on fuel filter has a gauge on it that is reading 9 lbs at idle- Is this right, or will it cause problems?

 

[doghead]

Do you have a stock pump?

 

[edpdx]

LIft pump? new per TM part number
IP? I've never touched it. I bought the rig with 56K on it.

 

[doghead]

If your lift pump is new, I'd guess that's the correct fuel pressure.

Why are you asking this question?

 

[TGP (IL)]

9 lbs. is normal for a stock pump and the system.
Your problem is elsewhere.
Tom

 

[Drock]

Well your evidence points to a fuel issue. The question is what is it? Could be bad fuel, or a fuel pick up and delivery issue. At this point I'd just drain & drop the tank, then replace the fuel pick up components & hoses. How old is your lift pump?

 

[doghead]

Merged with original problem thread.

Next time please ask relevant questions in your existing thread.

 

[edpdx]

Merged with original problem thread.

Next time please ask relevant questions in your existing thread.

OK, I will. I asked because I just installed a new Holley fuel pressure regulator on my wife's Mercury 2v Cleveland. The pressure called for was 3lbs. Having spent so much time under the hood of my blazer, I thought 9 lbs was either too high, or the 3lbs was too low. Injectors vs carbs I guess.

 

[edpdx]

Well your evidence points to a fuel issue. The question is what is it? Could be bad fuel, or a fuel pick up and delivery issue. At this point I'd just drain & drop the tank, then replace the fuel pick up components & hoses. How old is your lift pump?

Drock, I am thinking I can find the same result if I disconnect the supply line to the fuel filter, and replace it with a line from a fresh can of diesel. I'll do a filter swap so only fresh gas is supplied to the IP. Good idea, thanks. I'm off to get a new fuel filter.

 

[rsh4364]

Same symptoms I had last August, I replaced everything in the fuel system, it ended up being the injection pump.I suspected someone dumped something in my fuel tank, so the first thing I did was replace the tank,sending unit, fuel lines,lift pump, fuel filters and injectors. The smoking loud knocking persisted until I finally replaced the IP. Another symptom was revVing the motor up and letting off the throttle and motor would struggle to regain idle or just die..

 

[edpdx]

I decided to drive over to Oregon Fuel Injection to have them verify failing IP. I have an appointment for Wednesday.- The drive is one hour from my home. The service desk guy said he DID NOT have the DB2 829-4521 pump on the shelf. He did say the alternate part in the book is DB2 829-4502 (he called it the civilian upgrade). He says the OEM 4521 pump is 12 volt- does that sound right?

Question: Should I give him my 4521 as a core ($300), or eat the core charge and have the 4521 rebuilt with hardened parts later?

Is the IP really 12V?

 

[rsh4364]

Yes,12v. I would pick up a core online somewhere, usually run 50-100$.

 

[edpdx]

Dropped my Blazer off nine days ago at Oregon Fuel Injection. Picked it up yesterday. I had the OEM IP rebuilt. They found related timing for issues. Just over $1600. Runs great. Thanks for all the hard input. With all the clatter I was sure it was rod knock. Hoping I’ll have smooth sailing for awhile.