Another "longer starting" thread
 

1998.5 2500 almost completely stock truck. 225,000 miles.
No gauges.

Recently, when warm, the truck has been having the long 5-10 second start issue after it's been run for a while. It seems like the shorter time it's been off, the more regular the problem becomes.

I have a low fuel pressure light that indicates less that 5lbs between the filter and VP44. Yesterday I ran a few errands around town and these are the results;

At cold start I hear the lift pump cycle but the pressure does not exceed 5 lbs. Truck starts great and after a couple of seconds the pressure exceeds 5 lbs and no matter how hard I run the truck, it does not drop below 5 lbs. This indicates to me that I am not exceeding the flow of the lift pump or fuel filter.

After being shut off for 5 minutes, the low pressure light is on again at start up and the engine cranks for several revolutions without catching. Mind you, this truck has always fired about as fast as I can turn then release the key. After releasing the key without start, returning to to the ignition position, the truck will wait a second, then cycle the lift pump and show the 'wait to start' light. At this point the low pressure light goes out about 50% of the time, and regardless, the truck fires as normal.

After being shut of for longer than, I don't know, 15 minutes, it fires up without issue.

I'm starting to think that the pressure is bleeding out of the fuel system when the truck is not running. I have no fuel leaks, don't know what the fuel pressure is other than knowing if it's above or below 5 lbs, and can hear the lift pump properly cycling when expected. I realize that this is not the ideal diagnostic situation and that gauges and some non-stock lift pump would be better, but I don't have them.

I'm leaning toward the fuel overflow valve needing replacing since it's probably the original. Also, I wonder, is there a ball check valve in the system at the lift pump or fuel filter and could this be a place where the pressure is leaking back into the tank?

Thanks in advance for any help/tips.

Not sure if related - but I use to have a hot-start issue. On warm days when running for an hour or two, then shut down... when I went to restart 15 minutes later it would crank and sometimes almost catch, then finally lite!

When cold, would lite up right away - no issues. It was just when everything was pretty hot.

Don't remember where or why, but I swapped two relays under the hood. The fuel pump relay and the fog light relay. Both mini relays I believe.

Have never had the hot-start issue again and that was 5+ years ago. Just throwing it out there.

Thanks, I'll give that a look.

Anyone else want to chime in?

Something to try is to bump the starter and let the lift pump run for the 25sec then try to start the truck and see if it starts faster if not have to look at the battery and see if they are weak.

Changing the relays worked for me to,only to start the hot start problem again.The underlying issue was the insulating material stuck to the bottom side of the hood was getting droopy and insulating the heat in,especially at the fuse box and the IP.The problem disappeared.

Is this the original VP? If so, its been through its fair share of heat cycles.....and your lower than desired fuel pressure isnt helping. Next time you think its going to hard start when hot, pour a gallon or more of cool water directly on the top of the VP and then see if it starts more normal. If so then the VP computer is showing signs.

I am having very similar problems. Have a 98.5 2500, 5 speed, 2WD. Have gauges though so I can see what is going on, stock VP. Last year when I finally put gauges in the fuel pressure would go from 10 down to 2-3 when I hit the gas. I changed out the fuel pump on the block and that worked for about a year (would have between 9-12 pounds of pressure) until last week it went down to about 5 psi. I warrantied the fuel pump and they gave me an airtex one this time (the last one wasn't an airtex just a stock replacement). Just replaced it and the fuel pressure is still at 5 psi. Sometimes after driving it it will creep up to about 9 but everytime it starts it will be in the 5-6 range. Any ideas? Are the Airtex pumps just junk?

They can be just as bad as the OEM Carter lift pumps. But there are guys who have good results from the Airtex. Small fuel line diameters and restrictive fuel fittings are huge contributors to weak pressure.

Am I OK as long as it keeps a steady 5 psi? Obviously it isn't ideal.

ABSOLUTELY NOT OK.
first i installed a 5 psi warning light but i felt like i was still in the dark not knowing what was going on and would flash red going up the hills.The gauge came next and has been a terrific diagnostic tool.You,ve got some stuff going on there with those changing pressures.Five psi is really an absolute minimum,you need to be up to 17 or 18.If your going to fix it you might as well go for an optimal pressure but don,t wait,because a 5 psi reading cost me a pump and $2000.

The absolute lowest fuel pressure the VP should ever see is 10 psi. In saying that, I will continue by saying that 10 psi is too low as well. Staying at or above the preset 14-16 psi of the overflow valve is important. The 5 psi warning lights are worthless and only tell you when the fuel pump is pumping little to no fuel. Dennis is right by say that gauges are much better diagnostic tools.

Katoom ,is the overflow valve what some call a Banjo bolt?I see where the incoming fuel enters the VP then right beside it is the return line,what i,ve always known as a banjo bolt,following the return line to the back of the engine it tee,s off one side going back to the tank ,the other looks like disappears behind the engine block.
Another question ,if you took a NEW vp44 and heated it up beyond it,s limit,would you experience a hard long cranking hot start,or no start due to a RESET of the electronics.

Yes, the overflow valve is a banjo bolt. The inlet and the outlet ports are right next to each other. The return line coming out of the overflow goes back to the "T" fitting you saw where it combines with the excess fuel line from the injectors which comes out via another banjo bolt on the back off the head. Both join at the T and then run back to the fuel tank.

Regarding your question about the VP..... I'm not sure. I guess it would depend on what was damaged, if anything. The computer electronics connected by lead free solder are the weak link with heat and are the most likely to cause hard start problems after over heated. Here's a picture of what the lead free solder does.

http://i530.photobucket.com/albums/d...psc69626d5.jpg

What is weird is that it went from a consistent 10 psi down to 5 psi. Changing out he pump didn't change it at all, maybe some junk in the line? Any other suggestions? Towing from Seattle to LA at the end of the month and need to get this fixed.

The overflow valve can be replaced easily - Geno's garage sells them at a reasonable price.

I will defiantly replace the banjo bolt as my vp will not except a pressure over 20.I have been doing some major research about under the hood temps and solutions.But to more accurately define the problem of overheating tendency of the vp, this is what i came up with.The VP is completely tucked in behind the gearing and gear case,it is completely out of the airflow of the fan.I like the double electric fan from flex lite and control from the cab,under the hood temps.I also think it possible to rig up a strong little fan from underneath and duct it strait into that dead air pocket under the vp.Oh yes defiantly remove puke boodle and clean oily residue off radiator.Also i think it a big mistake to be using hot under the hot air for engine intake.

As usual dennis, I understand and respect your desire to solve VP issues, but really the items you're after in that last post are mute. Why?..... Because the VP doesnt have a problem while the engine is running. So why care about anything pertaining to this? Yes, the VP kinda sits behind the timing case but given the amount of air passing through the engine compartment, its not a problem. If you want to pursue a fan to blow over the VP "after" shutdown then great, I think others will be all for that. But again, you'll find that electrical drainage on the batteries is going to be a problem, and finding a timer which can handle not only the amperage but the amount of time you'll need.

With regards to that, I can add some input to the fan after shutdown thing and what I did and what I experienced. After coming home on hot days, I open my hood and leave it that way until everything has cooled some. But.....I used to also prop a small house fan on the engine pointed directly at the VP so as to aid the cooling of the VP and deter heatsoak. After doing this I had the engine do some REALLY weird stuff the next day. I started the truck and all of a sudden the engine shook violently and a loud hissing noise came from under the hood. Coincidentally the fuel pressure read ZERO too. I immediately shut the engine off. This was back when I had an electric FP gauge so I can only guess that it was telling an accurate story and not a reason for some electrical glitch. This event only happened twice with no particular time or reason other than the fact that I cooled the VP with that house fan, but it was so odd and violent that I opted to let the VP cool on its own and see if this happened again. No, it did not.

I couldn't tell you what actually happened or what I was hearing since both events were so quick, but I can absolutely tell you that it had something to do with the VP. Believe it or not, I thought for a second that the engine was running backwards. :o

Lastly, you not liking the heat under the hood for intake is the wrong approach. As we talked about before, diesels are not gasoline engines and NEED heat to function properly and complete combustion. Especially the 24v engines. Thats not to say that drawing intake from an extreme heat source is best but that the air from under the hood and the air from the cool source in the fender is perfectly fine. The cold air intake systems for diesels are marketing tools to make people buy what they think they need. Matter of fact, cold air intakes and huge exhaust systems can turn out to be negative attributes in the winter and for guys who drive in the frigid climates. There is far more to this topic but I'm just trying to point you in the right direction. Keep up the good research about VP's though.

well..
to take matters in different and costly direction..
first your fuel pressure is low..most likely not the overflow valve..sorry
hard starting..
follow Blue chips VP44 diagnositc chart..on this..YES it applies.

worst case you looking at a new ECM for the engine.$800...
sorry..had hard starting..lift pump not starting issure this summer..almost didn't get home..that bad..dreaded the thought the $800 would fix the problem..tried just about everything else..then changed the ECM..problem gone..

so does you lift pump the instant you turn on the key? it should..yes always!
yes it will turn off almost instantly..but it runs at key on! then pulse runs until its running..ok so bypass the lift pump( on all the time) does the truck start?maybe the ECM isn't turning the on the power to the VP44??
follow Blue Chips..and go from there..

-dkenny