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Cummins 300hp 8.3 Fuel System Overview

Time:2018-02-07 16:23Turbochargers information Click:


This engine has a mechanical injection pump and a hand operated plunger type of a fuel primer. There is no Electronic ECM on this engine.

I got out yesterday to start the coach and move it to another site. The engine turned over just fine but never caught. No smoke - just cranks. I have plenty of fuel. There is fuel in the primary filter - at least it comes out the bottom. It started fine and I ran for about 50 miles a month ago. I put a call in to a Fleetcare shop and he said probably a sensor but they would need their computer. After I explained that it was the mechanical 300hp 8.3 (again) He said he would check (with someone else?) and would call me back. What sensor and where is it? We have had mice around. What next? Any suggestions? Elliott & Mary Bray 1996 36' U295

Between the fuel filters and the injection pump is a "fuel return valve"; when it fails, it allows fuel to leave the injection pump and return to the fuel filters. It's on the passenger side near the injection pump, but I can't tell you specifically where it is because a diesel mechanic showed it (defective one) to me after he had replaced it. It's not large nor expensive. The other possibility is the "fuel cutoff" solenoid which is in the same vicinity (passenger side, ro right of oil fill on side of engine). If the solenoid (electromagnet) fails, fuel won't flow to injection pump. A little more expensive, but not really labor intensive for a real diesel mechanic.

Both the fuel return and fuel cutoff solenoid on my 8.3 died within a few months of each other when my coach was 15-16 years old, similar to the age of your coach. Don Hay '92 Grandvilla, U-280

FIXED !! The fuel shutoff solenoid had become stuck - whether from old age or a piece of the ragged rubber boot had lodged in the armature. In any event. I was able reach it and turn the plunger and free it.

Then I had to give it several attempts of cranking for ~20 sec followed by 5 min. rests before fuel got back into the engine. Elliott & Mary Bray 1996 36' U295

Glad to learn that the fuel shutoff solenoid was just stuck. If you ever get in a bind and it won't lift the lever up to start the engine, you can use a long, heavy-duty black cable tie (12-18" long), wrap it around the lever, tighten it up and keep it that way till you get home. When mine died the mechanic gave me such a cable tie and showed me where to put it for future use. The only problem is you have to cut the tie to turn the engine off, but at least you can travel to get it home or to a service center. I keep a couple of those ties in my tool box just in case. Don Hay '92 Grandvilla, U-280

If the solenoid hangs up, it could be a broken spring inside. If you do not replace the unit, another problem could arise where the solenoid opens enough to let the engine start, but won't allow the rack to increase fuel as you try to increase speed, resulting in what would seem to be a huge loss of power exacerbated by the fact that you will be able to hear the click as the solenoid gets electrified. It is the 12 volts that keeps the solenoid open continuously.

It is almost too simple to describe. You can actually remove the solenoid with 2 bolts and a keeper spring. Once off, you will see the actuator lever for the injector rack. Simply wire tie or bale wire it wide open. The engine will then perform normally. Twig 1994 U280 40'

The fuel solenoid on the C series has two coils inside, one is the pull in coil, it hits the switch and the hold in coil holds it in, while the pull in coil is released (disconnected). The pull in draws about 20 amps, the hold in coil drawsn about half amp.. Keep your fingers away when you energize it, or it will hurt you. In our business, we every few years remove it, clean up, lube the slide with silicone grease and reassemble, check the amp draw. Dave M. 2001 U320 36'

Fuel Shut Off Solenoid Replacement

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