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Hard Starts When Hot Out

2K views 19 replies 7 participants last post by  JMJNet 
#1 ·
Whenever it's really hot out like 90+ degrees I have a hard time starting my truck. ( 97 chevy Tahoe ). First start of the day is fine but if I go somewhere for a hour I have excessive cranking and sometimes have to cycle the plugs a couple times. Never had a problem till the summer.
New parts 10K ago are turbo, Heath pmd and injection pump, batteries, fuel filter, lift pump and acdelco glows.
It hasn't left me stranded yet thank god but I want to figure it out asap. I know the bottle of water on the IP trick so I have one in the truck just in case haha. I'm thinking it's the glow plug system isn't staying on long enough? Thanks
 
#2 ·
More than likely you have air in the fuel system.

How to Test For Air In Fuel System: http://www.dieselplace.com/forum/63...uel-filter-stalling-no-start.html#post4327423

Picture of Clear Return Line Installed: http://www.dieselplace.com/forum/63...-5l-td-pmd-resistor-settings.html#post7305306

How to Pressurize the Fuel System To Check For Air Leaks:
http://www.dieselplace.com/forum/63...ine/763698-air-fuel-gremlins.html#post7603650

Also, try unplugging the Coolant Temp Sensor to the ECM located on the coolant crossover before you start cranking to see if it helps.
It will fool the ECM to activate the glows longer, just plug it back in after it starts..
 
#3 ·
Thanks for the reply, I installed a clear hose to the return line and there were no bubbles just the one at the top of the hose that was there from startup. Also at idle I have just under 5 psi but falls to zero a while after shutdown.
Outside temp today is 88 so it's not giving me issues today.
 
#4 ·
Load test the batteries one at a time?
Battery can have a heat soak effect where the amp-acity is actually going down as the temperature is going up.
 
#5 ·
I replaced both last winter but disconnected and checked them anywise and both are good.
 
#6 ·
Starter thats been abused and mistreated eg severely overheated by excessive cranking, will often work OK when cold but fail to deliver the 'umph' and/or necessary minimum cranking RPMs when s'it gets hot..

The entire 'Electrical System' must be 100% to avoid driveability problems, PCM ghost and PMD goblins.. Batteries, cables, starter, alt, multiple harness's, dozens of electrical connections, and numerous critical grounds.. Assume s'its all good at your own risk..




It could be glowplug malfunction but I agree with OK, air leak most likely.

TIP: After a couple three months of heat cycling, be sure to go back over the new fuel injection system, especially if you replaced all them rubber hoses routed under the intake and FFM housing... Check for kinked, twisted, pinched, and/or improperly routed hoses as you retighten the clamps after the hoses become fully aclimated causing the clamps to relax there grip a bit when warm. Eventually hard cold starts will follow..


Thanks for the reply, I installed a clear hose to the return line and there were no bubbles just the one at the top of the hose that was there from startup. Also at idle I have just under 5 psi but falls to zero a while after shutdown.
Outside temp today is 88 so it's not giving me issues today.


Your LP output is sadly insufficient to keep up with a healthy DS4, possibly wrong LP model (reccommend ACDelco EP158 only) and/or damaged LP if its power or fuel supply is 'compromised' in any way. If the fuel system is airleak free and the liftpump is 'healthy', the fuel supply system should maintain 3 or more psi when not in use throughout the day..
Certainly shouldnt drop to zero in a few short minutes after shutdown, after several hours maybe....

FWIW. Restrictions, air leaks pre-LP, WTFE will 'hammer' the LP, beit brand new or decade old, to a swift premature death..... and 'sighting' the return oil circuit is hardly checking for airleaks pre DS4 pump.. If it were only as easy as relocating PMDs.....
 
#7 ·
Any lights flashing on the dash? My 2000 started this and the security light on the dash blinks... truck wont start until the flashing stops.
 
#8 ·
Thanks for the responses, I'm unsure of how old the starter itself is but the starter solenoid, batteries, 2/0 wires and connectors are all new along with all new grounds and grounding straps. So maybe the actual starter motor.
I did replace all the rubber lines with the IP but did not go back and tighten the clamps. Sounds like I may be removing the intake this weekend if it's not to hot out.
When I replaced the lp it was with whatever advanced auto had because they did not have the acdelco in stock at the time. With key on its at 5 psi and under 5 at idle. Could the lp be allowing fuel to drain back to the tank?

No there are no lights on the dash except for me ses because of my egr.
 
#9 ·
Just a note, I hardly seen any AZ or Advanced or Napa or PB or OR with ACDelco part in stock or even available through them.

You either go to stealership or order online.
 
#10 ·
On DS4 models, no need to remove the lower or upper intake manifolds to check on or tighten any rubber hose clamps. Its possible to R&R all the fuel systems rubber hoses without removing either intakes too..
Remove two bolts securing FFM housing to the intake, then carefully lift up to gain access to those concealed FFM connections. The IP inlet and outlet are easily accessable without major disassembly.. May be hell on the back, but so is R&Ring the intake needlessly..


FWIW.. Walmart (on line) can get most if not all ACDelco parts for less, w/ free shipping to your local store for pickup..
 
#11 ·
Actually, one of the reason you may want to open the intake is to check the IP harness.

There are a lot of member with that issue lately with similar symptoms to yours.
 
#12 ·
Thanks for the tip, unfortunately while I had everything apart I added a T after the FFM for my gauge so I don't think I can get to those. Maybe by feel and a stubby screwdriver.
Could the fuel pump be a problem with allowing fuel to drain back to the tank after shutdown?
 
#13 ·
Could the fuel pump be a problem with allowing fuel to drain back to the tank after shutdown?
Yes, internally the fuel in the Lift Pump could bleed back causing the hard starts..
 
#14 ·
Acted up again today. Tried unplugging the cts and that didn't help. When I turn the key to run the fuel pump goes up to 5 and when it automatically kicks off it falls to 3 in seconds and over a half hour goes to 0. Lift pump or air leak? Or both?
This weekend I'm going to tighten everything up and if that's not it I'll order a pump again only this time acdelco.
 
#16 ·
Of course, as soon as the engine turn off, LP turn off, the LP pressure will go to 0.

What are you expecting? No pumping motion anymore.

What is bad is when engine is on, LP should be pumping but no pressure aka 0.
 
#17 · (Edited)
Provided a healthy DS4 injection pump and a positively sealed fuel supply system, a healthy lift pump (ACDElco EP158 reccommended) should maintain 3psi or more INDEFINITELY. Certainly longer than 30 minutes... My recently restored fuel supply system still hold 4psi for several days after nearly 8 months of service.. Has drop'd to 2psi once after 7 days, longest period its ever sat undisturbed..

I suspect system pressure would drop to zero ie equalize to atmosphere after 10 days or so.
The service manuals mention releasing residual fuel pressure before servicing the fuel supply system eg FFM element replacement. Probably to remind the recent vo-tech d-tech grads that the 6.5TD's fuel supply system is usually pressurized soon after being driven into the service bay. assuming they use it. pfft who are we kiddin'

Also worth noting that a healthy liftpump wont permit fuel to drain backwards, towards the tank when not in use. A well worn liftpump's one way check valves may relax after a decade or two hundred thousand miles and wont maintain positive fuel pressure as long however given a sealed system so atmosphere (air) cant enter to displace the fuel, the fuel will remain suspended and cant drain back to the tank when inactive for extended periods...

Damaged and/or lazy lift pump one way(s) check valve(s) can also contribute to fuel aeration, as each valve relies on the other to maintain pressure during and between each stroke. Unlike rotary vane type lift pumps that operate at constant rpm, our solenoid type only pumps fuel on demand greatly extending its useful service life.

FWIW. Having 5psi with engine off, less with engine idling. I gaurantee you theres a problem and it will never maintain the 3psi min while cruising 75mph, especially when the DS4 starts slamming down the fuel to overcome gentle headwinds (slightest detectable increase in engine load), most often the operator is clueless of the DS4's binge drinking capabilities.
A new healthy ACDelco EP158 should be producing twice the pressures you have, mine does.. Your problem could be wrong LP, insufficient voltage, or restricted supply (suction) line assuming the FFM element is good.

Also worth mentioning the tee spliced into the IP supply for the pressure gage, fuel flow should pass straight through the tee with the gage connected to 3rd leg to avoid creating unwanted eddies so near the DS4 inlet.
 
#19 ·
Quick update, I replaced the lift pump with a AC delco. Fuel pressure is at 8psi and the hard starts are not at hard. Sometimes it has a little excessive cranking so when I get a chance I'm going to pull the intake and tighten up the fuel gauge T I added.
 
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