98 Hard to Start When Hot

[CedarGrove]

The wife's 98 dually is getting finicky on hot days. Seems it gets heat soaked in the afternoon. Won't start until it cools a bit (generally 30 minutes). She is a landscaper that does 2 to 4 jobs a day.

I was able to make it happen today. Had a 1/4 tank of fuel, temps close to 100 today. Ran some errands. Started fine after the first 3 stops (about 30 miles total). Last stop was a tank fill up ($101 worth). She refused to start. Poured water on the fsd heat sink and still nothing. Poured water on the pump and she fired right off. The pump from Pensacola Diesel has about 45k on it. I have some "marine injectors" from SS Diesel that have been there for about 50k.

I suggested to her that she keep the tank full through the dog days and hit the pump with some water if it refuses to start. Is it time for a new pump already? Time for the "marine injectors" to go? The ses light has been on for a while and I believe the codes are related to my pump timing. I really should get that sorted before I go too far but it has been running fine. Some mornings it is hard to fire off. Other mornings she hits right away.

Flight Systems FSD mounted on heat sink on drivers fender. It had been on the pump until 2 weeks ago (the one on the pump is still there, just slapped a different one on a heat sink). I don't think the problem is FSD related. I do believe it is pump related (fuel temp). The 3 times it has happened it has been on very hot days with less than 1/4 tank of fuel.

I need to address the rough fuel lines (as discussed in a different thread) and the pump timing. What else do you guys want to tinker with?

Lewis

[DmaxMaverick]

If you have to pour water on the IP for a hot start, you have 1 problem (actually, two 1/2 problems).

The "marine" injectors, typically, are calibrated to a higher pop pressure. Any condition that could cause the pump to produce less than this pressure, such as during a start (lower RPM), this "feature" will be exaggerated. The injectors are probably working as advertised, but are 1/2 of a problem.

These injection pumps will normally work well for a very long time (100-300K miles, or more). However, they live the majority of their lives in a state of "less than optimal". Having hi-pop injectors shortens the effective life of the pump. Replacing them with OEM injectors may allow you to use the same pump for a very long time. If you are able to get a start after some persuasion, you are probably operating at just beyond that threshold. Lowering the pop pressure may bring you back to the other side. If this doesn't improve your hot starts, your pump is probably on its last leg.

Make sure you don't have other gremlins in the works. Check for air leaks, or fuel contamination.

Get the FSD out of the engine compartment. It's worse off anywhere under the hood, than mounted on the pump (OEM style).

Try a set of OEM injectors. You may be able to just have your "marine" injectors recalibrated. Many/most who sell them use OEM injectors, and install a shim to increase spring pressure (the $20 shim). If they do, in fact, have "marine" nozzles, they won't work well. The flow rate and spray pattern will be off (inefficient) at lower pressure, which can lead to other problems (burned piston crowns).

[jonflies]

see my posts.

I installed "marine" injectors from SS Diesel on an engine with an IP that had about 70k on it, and it would not start when hot. Had to change the IP. After reading the previous post, I'm going to have my stock injectors rebuilt and keep them as spares, just in case.

[CedarGrove]

I have been stressed out about this problem for months now. Almost pulled the trigger on a new pump and stock injectors but just couldn't do it. The truck ran great once it started and besides that I don't have 2 grand laying around. Not real excited about spending 2 days wrenching either.

Anyway...I've been doing a load of head scratching on this and decided to drop the starter and have it tested. The starter failed. They gave me a new one for free under the lifetime warranty. Installed and things seem great. I feel like I'm good to go now. This is a serious amount of stress of of my shoulders and it feels great. I'll report back if things go down hill but I hope that I won't have to.

I am going to dig out the stock injectors and have them rebuilt by a Stanadyne shop and install those before the end of the year.

Now I can return to my fun project of getting my gov surplus 6.5 engine repaired and ready to go into my 84 beater.

How in the world anyone kept these trucks (and others) running before internet days baffles the crap out of me. These forums are absolutely an invaluable source of information and support.

[Robyn]

Once the engine is warm it takes just good RPM on the starter to fire it off.

During a hot start, if the IP is getting a tad worn the fuel gets thin and it can take a little more ooooomph to get the thing to fire.

A cold start has cold (Thicker) fuel plus the glow plugs to help fire it off.

Also when the injectors get a tad worn they don't spray as nice and in conjunction with a slow starter can make a warm start (not cold enough to get the plugs working if it has an inhibit switch) a bit dicey.

Glad things are working for you.

Missy