Won't start when warm

[Paul Amestoy]

I have fixed most of the problems with my 98 Suburban 135K.... Most having to do with power and remoting the fuel control unit. The problem I have now is that once the engine is warm it will not start.... It takes 10 minutes of 15-30 second turn overs to finally get the thing to fire...batteries at that point are almost dead... in the morning when cold it start right up....seems that the lift pump is working
any ideas?

[charliepeterson]

The next time it won't start try pouring tap water onto the Injection Pump. When these pumps get tired and heat up they loose internal pressure. The Injectors need lots of pressure to open. The tap water cools them down just enough to get them going again.

Too bad you're out of warranty by only 15K.

[Paul Amestoy]

Put in a new pump at 117K ? do you think the internal presure change from cold to warm would
not create enough pressure? ....

[kowsoc]

What happens is the hot IP has greater internal clearances allowing more leakage of high pressure. If the cranking speed is slower than normal, there is more time for leakage. Too much leakage and the injectors will not get the typical 1800 psi required to open, they don't pop, and the combustion chambers see no fuel. These engines need good cranking speed for hot starts. What condition are your batteries and starter in?

Also, where did you mount the FSD? A heat soaked FSD mounted too close to the engine will also cause hot starting problems. You could try tightening the power transistor nuts as stated in the PSD/FSD post.

Good luck, keep posting if you need more help...lots of good info on this site! smile.gif

[Paul Amestoy]

Thanks for the info...i mounted the FSD high on the drivers side wheel well... seems to get good
air.... May install a fan directly onto the heat
sink.... I just charged both batteries last night.. one is two weeks old the other about 6 months... I did find that changing the grounds and using the top battery connectors has really helped in starter speed.... funny my wipers work better.... I do find that my speedometer indicator swings when I depress the brakes... I am looking for the inst cluster ground... I recently found that the ground on the pass side behind the glove box was not really grounded...so I ran a dedicated 10gauge ground from the battery and things seem to run much better. Since you folks seem to know more than the dealer (lots more) I would like to put a Raycor filter in line toward the rear of the Burb...( do you have a model number )... Where is the rear fuel pump in a 98 K2500 suburban?

Thanks in advance tongue.gif tongue.gif :rolleyes:

[ucdavis]

If I get the facts right, you have new IP @ 117k, & have relocated the FSD to the wheel well, and now have 135k. If its a new pump then internals should be OK, but FSD could be suspect even after this low mileage, sorry to say (but that may not be the culprit).
I'd start w/all grounds in engine compartment, then under dash (incl. to PCM). Undo them, brighten them up w/wire brush, & tighten using a no-ox grease. Sometimes an internally corroded (can't see it from the outside) battery cable is the culprit, so if you suspect that you'll need to bypass or replace the cable; usually you can see some small amount of corrosion on the copper that is exposed, or at least a bulge or crinkle in the insulation a few inches from the exposed end.
If that doesn't get it, go to connections:
Did you make you own extension harness? If yes, I'd check all elements to see you're gettin full contact, all connections are 100%, etc.
Undo & check 15-pin connector by fuel filter, make sure all pins are clean & seating.
Then (you'll be glad you've got remote FSD now) undo FSD from heatsink & remove plastic caps from back (2ea.) & tighten the 1/4" nuts (finger tight using a bare socket then 1/8th turn); reinstall caps & FSD & check starting.
Good luck.

[Paul Amestoy]

I am thinking of replacing the older battery...do you know what each battery powers?... It really bugs me that it starts so well in the morning, or when cold, but will not when warm...... I am thinking that it could be the fds assembly, I will tighten those nuts tonight replace one battery in the am...and go from there.... I found 6 Ibs of presure from the lift pump and tons of flow...btw I had that replaced at 119K... and fuel tank cleaned....

[Marty Lau]

Paul;

Start with what UCDavis suggests, and try taking the FSD off the cooler and making sure the nuts on the trasistors (4 nuts 1/4in.) are tight and then make sure you tighten the mounting screw to the cooler real good. I was having problems and did this and it helped and others have too and seems to help.

[DAVE FERENCZ]

I HAVE THE SAME WARM START PROBLEM. I DISCOVERD MY LIFT PUMP FAILD. REPLACED IT. STILL HAVE HAARD WARM START. NOT AS BAD. I HAVE NOW LEARND. A FAILD LIFT PUMP WILL CONTRIBUTE TO HEAT ON THE PMD
IT WORKS HARDER WITHOUT LIFT. I KNOW IF YOU MOUNT YOUR FSD ANYWHERE YOU MUST HAVE A MACHINED FLAT HEAT SINK. AS WELL AS AIR FLOW IF YOU MOUNT NEAR TIRE THATS GREAT WHEN YOUR MOVING BUT NOT AT IDLE.
FSD WILL FAIL WITH HEAT IT GENERATES. ALSO WHEN YOU SHUT DOWN YOU STILL CAN HOOP IT. I WANT TO KNOW WHERE TO GET THE BEST PRICE ON FSD/PMD WITH COOLER AND APPLIANCES.

[Paul Amestoy]

OK get this....changed out both batteries with new gel cell type 800CCA batteries.... the truck fires up cold / warm / hot does not matter...seems that even though the batteries were new they seemed to dip below 12 v. when cranking and probably not generating enough current/volt. to properly feed the PMD... THat said the work of re-terminating the grounds has solved many problems...air cond. fan speed... I also had an air bag error that the dealer wanted $1700 to fix....funny re-ground the computer to battery ground and all those problems went away...

When it won't start try jumoering the system with another car ( that is running ) try it I bet it runs..