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95 chevy 3500 cranks excessive when cold

N

n01tk

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Nova Scotia
My 95 C/K 3500 turns over 10 times or more if it has not been started in the last 12 hrs. Before going to start position, I wait 5 secs with the key in the on position ( can hear the fuel pump running) and then turn it over. Once it starts the one time it starts quickly and runs very smoothly for the rest of the day. Goes into closed loop when up to operating temp.
Tried noid light when cold and noid light flashes but not brightly ( how bright should it be?) New fuel pump, lines, filter, TBI, and tbs. Any ideas?:mad2:
_________________
1995 Chevy 3500 deully dump truck
ECU 7427
MASK $31
31.xdf, 31.ads
 
Hopefully you have no air leaks in your lines.

Did you check each of your glow plugs? You can check the glows in the truck with a continuity tester. You can also check the glow plug wires from the controller at the same time.

Detach the glow plug wire and test the glow plug for continuity/ohms. test from the spade to ground. If the buzzer goes off or you get less than .02 ohms resistance you have a winner.

To check the wire while it is still detached from the glow plug - attach one lead to the output side of the glow plug controller and the other to the spade connector where it was attached to the glow plugs.

Have the timing checked?

It still sounds like a fuel drasin down issue to me. Maybe the fuel filter housing has a leak. Do a search here.
 
He's asking about a gasser but your comment about the fuel drain down does pretty much apply - in a different sense.

n01tk - when you replaced the pump, did you replace the short section of rubber line that connects it to the sender, too? If not, it needs to be done. That line deteriorates from the constant contact with fuel and often will crack or spring pinhole leaks that cause problems building pressure, and it usually exhibits first as a hard start when cold.

Next up would be connect a fuel pressure gauge inline where the filter normally goes and watch your pressure readings while you're trying to start cold. You didn't tell us if it's a 5.7 or 7.4 but since it's a 3500 dump truck I'll assume 7.4 - if so, '94 and '95 7.4's run higher fuel pressure than the older models, 26~32 psi is the spec.

Richard
 
A gasser? In that case you should start the fix by switching to a diesel.

try to give it a little cap of gas and see if it fires right up like that. If it does then you have a lag in your fuel delivery
 
Thanks for the replies. It is a 5.7 gas engine. I did replace the short rubber hose which connects the fuel pump to the line. I put a fuel press gauge in the line ( just before the TBI connection) The gauge reads 10 psi when running. Takes about 5 secs to pump up to that value ( key in "on" position with truck not started). When the key is turned off it bleeds down in ~ 15 secs. If I pinch the return line off with needle nose vise grips the pressure pegs the gauge and stays high indefinitely( engine not running but ignition in on position). Maybe a volumetric test of the fuel pump is in order?
 
While the fuel pressure book spec on the TBI small block (and also big blocks prior to '94) is 9~13 psi, if they're around 9~10 I'm nervous. Now, there could easily be some variance in gauges, especially on cheaper ones, that I could forgive maybe a 1psi discrepancy, but your 10psi reading plus the amount of time it takes to build that pressure tells me there's a problem.

When you turn the key on but don't start the engine, the relay should only run the pump a couple seconds to prime the system, and it should reach full pressure almost instantly and then begin bleeding off fairly soon after the pump shuts off. Some trucks were equipped with a "hot fuel module" that runs it considerably longer but these are fairly rare items and usually only found on vehicles that were destined for really hot climates.

I'm thinking the regulator in your TBI unit may have failed and it's preventing the pump from building adequate pressure. When you pinched the return line off you took the regulator out of the equation and the pump showed you it has plenty of pressure by pegging the gauge. A dollar says if you disassemble the TBI regulator you'll find a broken spring or pinholes/tears in the diaphragm.

EDIT - I did just go back and re-read your original post and you've replaced the TBI unit with a new one? Depending on how good a job they did of rebuilding it, could still be a regulator problem. Some rebuilders just replace whatever part they "see" is bad, clean the thing up, and throw it in a box.

I don't think I saw where you replaced the filter though, I'm assuming you've done this.

Richard
 
Yes, this is a rebuilt TBI. The orginal was in bad shape (water damage, corrison & rust) but regulated at 12 psi? I was surprised to see 10psi (checked calibration of gauge). I did install a new fuel filter.
Should the fuel supply line be full of fuel after the truck has been sitting? I would guess yes, and the pump would only have to add a small volume to bring press up. Even after running the truck,turning it off for 30 secs, than turning it back to the on position the pump runs 10 sec or more. The truck will start right up, weither you wait or not. It's got to be the unburnt fuel in the inlet or cylinders aiding the quick start. Thinking I will take the TBI fuel regulator apart and have a look, also may take fuel pump ass. back out of tank and check it over. The strange thng is the truck is doing the same thing as when I bought it (2 years ago), even after changing all these components?
 
What would make the pump run for 22 secs when initially turning key to on position ( timed with a stop watch). The ECM should pick up the fuel relay to energize the pump for 2 sec. Why so long?
 
That behavior sure sounds like it has a hot fuel module installed. I don't think it's going to be related to your starting problem, but I could be wrong. I haven't really messed with any vehicle that has that option.

Richard
 
Wondering if the dealer could tell me if I have the hot fuel module. The truck was orginally purchased by Pennsylvania General Works, seem to be a little far north to need that option but you never know. I have a buddy at the dealership who may be able to run the vin and give me an answer.
The signal " elec fuel pump in", what purpose does it serve? Thanks for the help.
 
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