Engine troubles during acceleration / cold start

[Christian Rokhgar]

Hi everybody,

I am from Austria/Europe so excuse my bad english!

My 95 Silverado

[Christian Rokhgar]

I found several related posts but found no answers for this problem:

"This a.m. the truck fired after just a couple seconds of cranking, but ran about half speed for 20 secs or so, then smoothed out. The truck then sputtered on acceleration for a couple miles, or until it warmed up."

"After a cold start-up, and while driving under light acceleration, I started to feel real "fishbiting"; a severe hesitation, grab, bump, whatever you want to call it. When it's really cold, I feel this condition for about 12 minutes of driving time...until the engine is close to operating temperature. The hesitation/bucking is very pronounced upon acceleration and I feel the fishbiting once I'm driving the truck at a constant speed"

Chris

[DmaxMaverick]

Have a look at some of TDP's member's articles. They are very detailed with troubleshooting tips.
Here's a list of some of them:

www.thedieselpage.com/members/tt99-9.htm (http://www.thedieselpage.com/members/tt99-9.htm)
www.thedieselpage.com/members/guide.htm (http://www.thedieselpage.com/members/guide.htm)
www.thedieselpage.com/members/trblcode.htm (http://www.thedieselpage.com/members/trblcode.htm)

Your problem does sound like a fuel delivery issue, but probably isn't an injection pump or PMD/FSD problem. A small air leak can allow air into the system while the engine is off for a period of time, like overnight. A failed fuel cap can also cause problems like this, and usually becomes more evident when the weather turns colder. A failing/failed Oil Pressure Switch can also cause these issues. I would suggest starting with confirming the lift pump is good, and work your way through the fuel system from there. If your lift pump has failed, the injection pump can, and will, draw fuel via the internal transfer pump enough to run the engine. When cold, the fuel viscocity will be higher, making this more difficult, and cause starvation. A healthy glow plug system is important, but shouldn't be an issue that far into running.

Good luck!

[Christian Rokhgar]

This cold winter mornung I had again these troubles with my 6.5Td as descirbed.

I opened the black cover on the fuel filter to let out air which eventually could cause the problem.

Belive it or not - all the troubles were suddenly gone. No "fishbiting" and no hesitation anymore!

I will check fuel lines with a preassure test. We will see.

Chris

[moondoggie]

Good Day!

Your symptoms are classic failed lift pump system, especially when you get a miss under power. As you say, it feels exactly like a gas engine with an ignition miss.

It sounds like somehow you got air in your fuel system & successfully bled it out.

If this reoccurs, there's actually some good news. You & I & others who own 1995 (yes, this only works on 95 trucks) have the easiest-to-test lift pump system, at least with the engine not running (this assumes you have an automatic tranny). To power-up the lift pump without the engine running, simply put the shift lever in any position EXCEPT Park or Neutral, & turn the ignition key to the crank position. The lift pump will receive power, but the engine won't crank. If you crack the air bleed on the top of the fuel filter housing, fuel should squirt all over the place. If not, your lift pump (mounted inside the driver-side frame rail) is either not getting power or has failed.

With a properly-operating lift pump & the engine idling, opening this same air bleed should also squirt fuel all over the place.

Keep in mind, your lift pump is powered through two circuits. During cranking, there's a relay that powers the lift pump; during running, the lift pump is powered through the OPS (oil pressure switch/sender). Sooooo, you really want to check the lift pump during both operating conditions.

You also might want to keep in mind, Thursday, 24 November, is Thanksgiving holiday in the US. Also, most folks get Friday off too. That might mean less responses; or maybe it

[Christian Rokhgar]

I changed the lift pump - nothing changed!

I will pressure test the fuel lines today.

Chris