Tech Q&A Part #5

Wait to Start…Is it Working?

Hi Jim,

I own a 2007 classic (1^st gen body style) GMC Sierra with the LBZ Duramax, which appears to have a problem with the glow plug system. The first indication of a problem occurred after I mistakenly cranked the engine before the glow system’s “Wait to Start” light had gone out. Since then, the “Wait to Start” light appears to remain ON for a much longer time when the engine is cold. When the engine is warm, the light may not come on at all. Does this sound at all normal? What would you recommend I do?

Thank you,

Leslie Maht
Via Email

Hi Leslie,

The GM Powertrain engineers knew that an owner likely would, at some point, attempt to start the engine before the glow system had completed a normal glow cycle. The glow system was designed to deal with this without causing a problem, except that the engine might not start as cleanly as it might have after having a complete glow cycle. I’ve done this many times through the years, either by accident or because I couldn’t wait. No problem resulted from doing so.

In a Duramax equipped truck, the “Wait to Start” warning lamp will illuminate when either the glow plugs or the intake air heater is energized. The glow plugs are ON for only a few seconds, but the intake air heater can be ON for a much longer time, depending on the engine temperature. If the engine is started near to its operating temperature, the glow plugs and the intake air heater might not energize at all. You’ll know when the glow plugs and intake air heater are ON by looking at your battery voltage gauge on the dash. When the heaters are ON, battery voltage will be 10-11 volts. When the heaters are OFF, battery voltage will be closer to 14 volts.

If you’re not sure whether your truck has had the most recent glow system reprogramming performed, a dealer could look up your VIN and tell you. If your truck needs this, it’ll likely be done at no cost to you – as part of an EPA required emissions update.

Medium Duty Dodge Speed Limiter

Hello,

I have a 2008 Dodge 4500 with the 6.7L Cummins. I love my truck! Can you tell me how to raise the speed limiter on my truck and how to squeeze out a little more power? This truck is my primary means of conducting business, and it almost always has an 18,000-lb. trailer behind it. Any help you can provide would be appreciated.

Thank you,

Will Haster
Via Email

Will,

The folks at U.S. Diesel Parts tell me that the Hypertech Max Energy Programmer comes up most often when asked about improving performance for the 2007.5-2009 Dodge 4500/5500 6.7L Cummins diesels. However, other advertisers here in Diesel World may be able to help as well.

The 4500/5500 6.7L Dodges are speed-governed at about 76 mph because the commercial-grade factory tires used on the medium-duty trucks are not rated for higher sustained speeds. For those considering buying new tires for their 4500, sit down with your tire dealer and spec out the tires you want on the truck. With a higher speed-rated tire, you should be able to bump up the speed limiter without fear of outrunning your tire’s speed ratings. You should also consider your trailer tire’s speed rating. Good luck, and let us know what develops.

Tranny Swap

I am considering trading the automatic transmission in my 2000 Dodge 2500 4×4 for an NV4500 5 speed manual. I already have the major parts needed for the swap, but I am not sure about the computer programming or anything electrical that might need to be changed. Assuming I make the change, do I need to consider an aftermarket clutch system? I already have the factory clutch parts removed from a salvage yard truck. Your help would be much appreciated.

Thanks,

Alex Warne
Dodge City, KS

Alex,

This is an expensive conversion when buying all new or like-new parts, but since you have already acquired all of the expensive components, here’s what I’d do.

The automatic transmission equipped Dodge used the NP241/271 4-wheel drive transfer cases that were equipped with a 23 count input shaft spline. The manual transmission equipped Dodges received 4-wheel drive transfer cases having a 29-spline input shaft. The 23-spline input shaft in the transfer case worked fine when used behind an automatic, but not the manual transmission. You’ll need to upgrade your transfer case input shaft as well.

Electronics – As is true for Ford & GM transmission conversions, I would either reprogram your original Dodge ECM to manual transmission specifications (your dealer could do this if you can provide them with a VIN for a manual transmission equipped truck that is otherwise similar to yours) or find a replacement ECM having the correct manual transmission programming.

The wiring used with the automatic should be secured so they won’t become a problem later on. I’d either seal the electrical connectors so they could be re-used at some point in the future or… I’d remove the transmission-related wiring completely.

Using the in-cab factory stock clutch pedal mechanism and related parts sourced from a salvage truck is an excellent idea. For a clutch plate, pressure plate and flywheel, the stock parts will do a fine job if you are running at or near stock power. If adding performance is a possibility, I’d go with an aftermarket set of components now while the installation process is underway. Any one of several advertisers here in Diesel World magazine will help you with Dodge clutch parts.

Two-Stroke Oil – Diesel Fuel Additive?

Hey Jim,

I own a 2002 Dodge 3500, 5.9L Cummins, 6-speed manual with 135,000 miles on the odometer. My truck is currently sitting at the local dealership having a new fuel injection pump installed. The extended service policy I have is saving me a bundle.

Pump wear may be the culprit behind the failure of my current injection pump. This got me to thinking…which brings me to a question that no one seems to have an answer for. What is the current thinking about adding 2-stroke oil to the fuel as a lubricant? Even those who agree that 2-stroke oil may help cannot agree on the amount to use or if brand name oils have any advantage over the bargain 2-stroke oils available, say, at Walmart. Lastly, is there any advantage to using any of the higher priced specialty diesel fuel additives in terms of fuel lubrication?

Would appreciate any advice or opinion you might have on this subject.

Thanks,

Dale Burnette
Charleston, NC

Hey Dale,

Your 2002 Dodge Cummins uses the Bosch VP-44 rotary fuel injection pump. In general, rotary fuel injection pumps are somewhat more sensitive to both fuel lubricity and inlet fuel pressure.

Many believe that some portion of the VP-44 failures are due to a lack of inlet fuel pressure – resulting from either a failed or poorly performing electric fuel lift pump. Several vendors advertising here in Diesel World offer fuel pressure monitoring kits that warn the driver of below normal lift pump fuel pressure, allowing you to correct the problem before it results in an IP failure. BD (BD-Power.com) and USDP (USDieselParts.com) come to mind when looking for a fuel pressure monitoring kit, but there are many others.

2-cycle oil has been used with success as a diesel fuel lubricity additive. After all, this type of oil was engineered to provide lubrication in dilute concentrations and to burn during the combustion process. Many of the high-end 2-cycle oils are mixed at a 100:1 ratio for a traditional gas/oil mix for chainsaws and other high-performance 2-stroke engines. When used as a diesel fuel lubricity treatment, you could raise the ratio to 200:1 (20 ounces of oil per 30 gallons of diesel fuel) or even up to 400:1 (10 ounces of oil per 30 gallons of diesel fuel).

However, other than a potential to increase emissions, 2-cycle oil won’t contribute much to the combustion process. In an older non exhaust-catalyst equipped diesel pickup, 2-cycle oil will contribute to fuel lubricity without much of a downside, but there are better choices. Incidentally, 2-cycle oil should not be used in a 2007+ Diesel Particulate Filter (DPF) equipped diesel engine.

Just about everyone on the professional side of diesel fuel injection, who recommends a commercial diesel fuel treatment, agrees that a fuel treatment should contain a cetane improver, fuel injector cleaner and a fuel lubricity enhancer as part of its package. The use of a commercially certified product won’t jeopardize a vehicle warrant, and they can be used in even the newest diesel pickups. Diesel fuel treatments that incorporate a cetane improver may also improve fuel economy just enough to perhaps break-even on treatment cost. That’s what I use. DW

If you like the Q&A series, here’s the previous post in the series: Tech Q&A Part #4