slowly decreasing MPG

[Greg5OH]

I noticed over the past 6-8 months my mileage has been dropping, from 18/19 t0 14/15. Also noticed my EGTs cruising at 70 have lately been 700ish whereas before they were 500-600 doing the same route to/from work. Sometimes I hear a louder noise from the engine at idle. Could it be a sticking injector? If so can I pop them out and put them in an ultra sonic cleaner? Don't know anyone with a pop tester around here but maybe I will build one.
These are stage 1 injectors from R&D and have approx 15k miles on them if not less. So, pretty new.

Could it be a failing IP? no idea how many miles it has, and it does have a very tiny weep from where the accelerator pump pin at the bottom of the housing goes into.
But I do mean tiny, as in there is no puddle or anything in the valley.

 

[OLDBULL8]

pump pin at the bottom of the housing goes into.

That's the Mechanical Advance arm. There is no accelerator pump on/in an IP. There's an o'ring in there, just difficult to replace.

 

[Greg5OH]

^thanks for the clarification. This arm does move with throttle input though.

 

[hesutton]

Timing? Timing will change with mileage on the IP and the injectors. The injectors could use a bit of time on the pop tester. If they open too early or leak.... things get funky like you are describing. Change in smoke (especially on decal/start up/idle), more cranking to start? No clue what he does, but if it is anything like Ken did with "stage 1's" my guess is your injectors are not going to show good things when tested.

Heath

 

[Greg5OH]

These are definitly not like Ken's. These injectors ran awesome as soon as I put them in. I had pensacola injectors in there and the truck plain sucked. I put Justins in and it started right up and idled completely smooth. There are a few others over on FTE that run justins injectors and are very happy with them. And I know for a fact I was gettign 18/19 mpg with these same injectors before.

I do have blue smoke on startup, goes away in about a minute, and no smoke when idling or pulling away (gently) when warm. Dont know if thats timing, injectors or i suspect valve stem seals. (closing in on 400k miles on the engine)
Im still leaning towards the IP wearing since its the only unknown mileage item I have on the truck. I timed it end of last summer I believe to 9 degrees, but like I said...who knows how many miles the pump really has. No hot start issues. Cold start is fine too (in summer temps) winter would need to crank for 4-5 seconds after a 15s glow.

 

[BDCarrillo]

Weren't stats posted recently on how lift pump pressure changes the timing of the IP? Might a slowly failing lift pump cause a decrease in timing, thus MPG?

 

[laserjock]

Timing can change as the pump wears too. If it is on it's last legs the effect may be bigger. See @Dieselcrawler video where he timed his pump not too long ago and to his surprise it was out again when he did the video on how to use the tech time timing meter. If it's getting lazy I would think that would retard the timing which I think could cause your symptoms.

 

[Greg5OH]

doubt it. Carrier lift pump. pumps the same as always.

 

[icanfixall]

As our injection pumps wear out the timing changes. Its a slow process but it is telling you this pump is turning into a crap fest. Might start looking for a good injection pump and replace what you have.. Be sure to get all the parts off yours before you ship it to whom ever you buy from. the E4OD has a few parts that must come off. the throttle driver for the TPS must come off and go on the new pump shaft oriented the same way or the TPS breaks.

 

[Greg5OH]

^thats what I am thinking. I dont think a failing injector would cause the slow progressive drop in power and rise in EGTs would it? Id imagine it would start knocking really loud and the truck would generally run like crap?

 

[Greg5OH]

also id want to say i swear the clatter is no where near what i remeber the truck to have back in the day. its pretty mild.
If i had my own timing meter id check! Dont want to keep renting Grys, it will cost me a fortune..actualyl the amount of times I rented it could have already bought one lol.Still got my eyes on ebay for a good cheap used one one day

 

[laserjock]

Might be worth advancing it a hair and see what happens.

Based on what you say and what I have read, I wouldn't be shocked if you don't start seeing heat soak symptoms.

 

[hesutton]

IP would be my number one suspect, but I'd seriously consider pop testing your injectors while you have the injection system off the truck. I've only had one injector ever get stuck and knock. Most of the time, the mileage starts to go, more smoke, not as crisp startup, EGT/mileage changes. Problem is, symptoms can be the same for a long in the tooth IP. Weak IP or weak injectors = timing changes.

Heath

 

[chris142]

Where do you guys find places that pop test injectors locally. Nobody around here does, just look at me weird when I ask.

 

[bbjordan]

Don't want to sound like "that guy", but you have already changed the fuel filter...right?