Help for the first timer

[JClarahan]

Well this is all new to me so be gentle. I have a stock 91 D350 AT no intercooler and no engine mods and gets about 16 MPG. I loaded up the horse trailer for the first time and took it for a spin, quite a disappointment. The vehicle was sluggish and the temp gauge went ballistic. I need the MPG's but need the power too. Any thoughts??? My first thoughts were to replace the the 2 core verticle flow radiator and water pump with a 3 core crossflow and the new style pump. A friend gave me a big Ford intercooler..... will it work? I have also herd that a 16cm2 turbine housing will help. Any help will be greatly appreciated!!!

 

[JLEONARD]

Personally I wouldn't dick with the radiator and water pump until you get the power up to where it should be.

Then see if you have a temp problem.

Fuel filter is frst to make sure that is ok, then go from there. AT probably has something to do with the sluggishness... . I'm a 5 spd guy so I'm no help there.

The AT guys also need to comment on the housing size question as it reacts differently than on a manual trans.

 

[rumblefish]

The radiator might be a good swap. My old early 91 (non-intercooled like yours) liked to get hot while pulling my buddy's truck to the truck pulls. It weighed 5500lbs, and trailer was maybe another 2500. Smaller loads weren't a problem. Before you swap it out, make sure it is not clogged up or anything. You should also put in an aftermarket temp gauge, the stocker is not exactly known to be reliable. If you are pulling much of anything, a large aftermarket trans cooler would be a good asset as well.

 

[dpuckett]

WIth a non-intercooled 91, I'd assume you have a 3. 07 rear axle, which is good.



Check the valve adjustment. This one gets overlooked by the average owner, and can have a BIG impact on performance.



Fuel filter, for the same reason.



flush your cooling system, get the radiator cleaned out, and change your thermostat, with a Cummins unit. Pricey, but the $20 saved wont buy an engine. I have no experience towing with the smaller radiator. The only nonIC truck I owned came with the big radiator, and engine temp was never an issue. ALso, the factory manual says that a reading close to the "H" isnt out of the ordinary. Dont panic if the needle gets 2/3 of the way across the scale. Watch it, but it isnt cause to pull over and let it cool off.



But, you have an auto, they are marginal to begin with, and as they age, dont get better on their own. A torque convertor and valve body upgrade may be in your future. The stock convertors are horrible behind a low revving engine, though I have heard the earlier ones did a little better than the later OD trannies.



I'd look into upgrading the cold side of your turbo before the exhaust housing. You have an 18. 5cm housing, and with an auto, will probably notice little to no improvement.



GAUGES, GAUGES, GAUGES!!!! I can not stress this enough. You need to know what is giong on inside your engine, and the only real way to know is to be able to monitor it. Exhaust temp, boost, and transmission temp are a bare minimum, with fuel pressure and a tach a close second.



Exhaust temp (pyrometer)- self explanatory. You want to know how hot your exhaust is coming out of your cylinders. You can learn to drive by it and sometimes gain fuel mileage in the process. (lower temps, lower fuel consumption)



Boost gauge- complements the pyrometer. Tells you how much power your engine is making (to a point, and it is relative, not absolute), and how much air you are moving through your engine.



Transmission temp- If your engine is getting warm, your transmission probably isnt far behind.



Tachometer- tells how many RPMs your are turning, and with an auto, can tell you if you have a horrible, sloppy torque convertor, or need to look elsewhere for your troubles.



Fuel pressure- Tells the supply pressure of the fuel system after the transfer pump (down on the side of the block, just above the starter). Low pressure can point to a bad lift pump, or a clogged filter. Or, in the case of the few still running the stock diaphragm style pump with a hotted up injector pump, when we are giving the engine too much fuel .



Injector condition can also influence fuel mileage. Was your pickup a cream puff, "never towed a trailer" or the like? If so, you may have some injector issues, like coking, clogging, and just plain wear. I have found that trucks worked hard, yet within their design limits, and maintained (oil and filter, coolant changes, along with prompt repairs) actually have better fuel systems than grocery getters. The fuel system is like our cardivascular system- good workouts keep it healthy.



I dont think 20-22mpg empty hwy and 14-17 towing a 4horse trailer is too much to ask, even with your lower gearing.



Daniel

 

[JClarahan]

Thanks for the replys, at least I have something to go on now.