Fish Bite on Warmup

[Big T]

Past two start-ups had some fish biting or stutter on acceleration for the first half mile, then it clears up. Any idea what the cause is? Time to change injectors?

 

[ak diesel driver]

Verify fuel pressure while driving

 

[Big T]

Verify fuel pressure while driving

That fuel pressure gauge is in Fullerton, CA and I'm 1,200 miles away in Stevensville, MT.

 

[ak diesel driver]

Could also be grounds/ poor connections

 

[jrsavoie]

6.5's should have a permanent. fuel pressure gauge.

It answers a lot of questions before they are asked.

Some questions can not be given a good answer without more details.

You could be having an unnoticeable leak down that takes that long to purge.

 

[Big T]

6.5's should have a permanent. fuel pressure gauge.

It answers a lot of questions before they are asked.

Some questions can not be given a good answer without more details.

You could be having an unnoticeable leak down that takes that long to purge.

That's what I was thinking: leak down. The injectors are near that 100K mile mark. Hard to know exactly as the PO had them installed. I bought the truck with 150K miles on it and it's now at 230K.

 

[jrsavoie]

I would be more inclined to guess leakdown on the other side of the IP.

It would still be a good idea to have your injectors tested and rebuilt.

Do you have a good rebuilder nearby or that you could ship to?

 

[Big T]

I would be more inclined to guess leakdown on the other side of the IP.

It would still be a good idea to have your injectors tested and rebuilt.

Do you have a good rebuilder nearby or that you could ship to?

I was just going to buy injectors from Leroy.

Not sure what you mean about leakdown on the other side of the IP?

 

[jrsavoie]

I was just going to buy injectors from Leroy.

Not sure what you mean about leakdown on the other side of the IP?

Anymore, I would not install new injectors without having them tested first. No matter where they come from. I've heard of people having one leaker out of 8.

You can have leak down on the supply side of the IP. Lines, FFM, etc. Often times a small amount is not noticable. The vacuum in the tank will suck a minute amount of air into the system.

 

[Big T]

Anymore, I would not install new injectors without having them tested first. No matter where they come from. I've heard of people having one leaker out of 8.

You can have leak down on the supply side of the IP. Lines, FFM, etc. Often times a small amount is not noticable. The vacuum in the tank will suck a minute amount of air into the system.

I have a couple sets of injectors at the Fullerton home. Would need to have those sent to a rebuilder, but need recommendations.

 

[Will L.]

You are way jumping the gun about injectors. Possible, yes so is 10 other things. Loading the parts cannon is almost never a wise choice.

Get a permanent mounted gauge on there, and get it tapped at the ip inlet with no rubber between sensor and ip.

Have someone else crank it while you watch the clear return line.

 

[Big T]

You are way jumping the gun about injectors. Possible, yes so is 10 other things. Loading the parts cannon is almost never a wise choice.

Get a permanent mounted gauge on there, and get it tapped at the ip inlet with no rubber between sensor and ip.

Have someone else crank it while you watch the clear return line.

Not clear how I would get a gauge sender in there.

I have the braided stainless FTB line from FFM to IP......and the clear return line.

 

[Will L.]

Ok, so watch the clear line on start up. If wife is at other place then set your phone on video and secure it well to record while you start the engine. Keep in mind when bubbles are only at start up, a bad check valve can be at play. Thats free and can do now.

On the braided ftb line- get a “T” between the line and ip. Put the sensor there. Mod mafia sells the fitting now, Leroy talked about he could get it, but not sure if he stocks it. Proper searching and you could save a couple dollars ordering direct if you find where to buy.

 

[jrsavoie]

I agree with not throwing parts at it. But if it is due for injectors by mileage, it will not hurt to have them checked. If they test good, all you are out is time and an installation kit.

There is a post on here about a rebuilder I and at least one other have used. No way of knowing if they are still in business, still doing 6.5 injectors or even still alive - for some reason I seem to be running into this more often as I age.

I have a couple sets of injectors at the Fullerton home. Would need to have those sent to a rebuilder, but need recommendations.

For injectors - The last time I used Diesel Injection Service LLC 430 54th St SW Grand Rapids, MI 49548 (616) 531-1030

With 2300 PSI pop pressure

 

[Will L.]

Yes if the 100,000 mile mark - ok. However, the possibility of new defective parts or rebuilt defective parts still exist. Properly diagnose is best action. If you put in new ones and 10,000 miles later it does it again does that mean put in new injectors again? What if it continues immediately. The worst case scenario is not just it still does it, but also does this other thing like maybe worse cold starts or smokes a little when starting.

Is that whatever the original problem getting worse, if injectors did they make it worse, or did you just add a new problem to the system, when before it was say bad check valve and now has pop pressure sent wrong or leaking pintle.

Thats why proper training and diagnostics is sometimes:replace with “known good”. It’s never replace with new nor is it replace with rebuilt....

Doing that (which a lot of guys do) is a gamble. It either fixes it or makes it worse.

This is different than you know the part you are replacing defective.

I say order the new ones and let them sit until you know this is a problem, or at least eliminate the most common issues around this.

 

[dbrannon79]

@Big T just an idea, but if you are nearing the 100k mile mark on your current set of injectors, I do remember seeing a write-up somewhere on rebuilding them your self. I know it isn't saying much for the issue at hand, but if you are able to test the other set you have on hand and maybe rebuild them, it could save you later having a spare set ready to install when the time comes. again, just a thought.

I agree with not firing the parts cannon until proper diagnosis is done. I was having the same fish biting your explaining and all it was was my lift pump was not working causing an air intrusion. 2x on checking the fuel pressure. if your near any auto parts houses you can rig up a boost gauge to check at a temporary test for pressure.

 

[MrMarty51]

I got one of these. Used a hose clamp and a short length of plumbers tape for a mounting, clamped the plumbers tape between the gauge body and the hose clamp. An already drilled tab sticking out long enough to use a screw already low in the dash above the Park Brake pedal area. I dont like having the live fuel tube in the cabin but for now its what I have until I can afford the money for an electro gauge and sender unit. I want to get a gauge that has boost and vacuum, in case the lift pump goes into a negative feed zone.

https://www.summitracing.com/parts/sum-800138

 

[Big T]

I got one of these. Used a hose clamp and a short length of plumbers tape for a mounting, clamped the plumbers tape between the gauge body and the hose clamp. An already drilled tab sticking out long enough to use a screw already low in the dash above the Park Brake pedal area. I dont like having the live fuel tube in the cabin but for now its what I have until I can afford the money for an electro gauge and sender unit. I want to get a gauge that has boost and vacuum, in case the lift pump goes into a negative feed zone.

https://www.summitracing.com/parts/sum-800138

Yes, I don't want a live fuel tube into the cabin. Please fill me in or recommend an electro gauge and sender unit.

I checked the clear tube on start-up and no bubbles. Ran the engine 2500+ rpm.

 

[ak diesel driver]

Your bubbles, sometimes very tiny, are usually easier to see at an idle.

 

[Big T]

Your bubbles, sometimes very tiny, are usually easier to see at an idle.

Did check at idle and no tiny bubbles.