Hard start fix

[rbr]

After trying all the hard start fixes with no sucess, I stumbled onto a way that works for me really well. I was eliminating sensor problems and when I disconnected the temp sender on the intake thermo housing just below the hard line and Voila, a good start! I hard wired a switch to the dash and shut the sensor off until it starts then flip it back on. If I forget to turn it back on, the SES light comes on and there goes my power. I replaced the sensor at first but had no change in hard start. I'm confused but happy...

[john8662]

Yeah, sometimes the temp sensor goes bad leading to a hard start, well REALLY hard start, crank, crank, crank, white smoke.

Makes you think that it's got bad glows, but it ain't.

Anyways, seems as though the is something else up.

Any other codes stored?

I'm thinking perhaps the pump may be out of time, this will give a hard start.

J

[twaddle]

Hi there,
Does it start ok when hot after running for a while?

Also have you tested the voltage at all glow plug connections and checked resistance of each glow plug or removed the glow plugs to check them physically and connect them to a battery to see how each one is operating?

Once the engine is running is there any power issues or signs of faults, smoke or rough running?

Regards and good luck

Jim

[rbr]

Yep, I did the glow plug resistance and all the other tests that are commonly known. I put a new sensor in with no change, that's the weird part, but if I shut the sensor off before start, I get a regular good start then I switch it back. I only have to use it on cold starts, that is if it hasn't cooled off to overnight temps. It's got me stumped and every one else up here too.
Thanks for the suggestions!

[rbr]

No other codes stored except one pump signal that has been there since I owned the truck and after it starts, I have as good power as most of the 454's I have had. No complaints.

[arveetek]

I did a similar mod. I installed a time-delay relay that breaks the circuit to the temperature switch when the engine is off, and then after it senses the engine is running (power from alternator), the relay waits about 30 seconds, and then restores continuity. This way, everytime the engine is shut off, the computer is fooled into thinking the engine is ice cold, so it advances the timing and fuel delivery to make a nice easy start, and then 30 seconds later, normal engine operation is restored. It's been working great for 2 years now, and I've never had a hard start since.

Casey

[rbr]

I guess that is the same result that I'm getting with a lot better explanation and a tricker way of doing it. Sure works slick doesn't it?
Thanks,
rbr

[gmctd]

Pulling the ECT connector results in PCM thinking it's -40degF outside - you get max glow time, full advance and more fuel - if that heals hard-start, you got glow problems or IP problems or fuel supply problems - or, even worse, all the above - could even be worser, tho: low compression

Glow plug resistance check is not the best test - pull each and connect to the battery with your jumper cables - each plug should glow from center to tip within 5 seconds - center-only glow is failing, will not provide enuff heat for cold-start, esp. in the gp harness - the glow plugs are actually 8v or 10v elements, depending on standard or quick-heat version - the harness is designed to limit current to them in a 12v system - if any gp won't full-glow in a direct-connect over-voltage condition, it surely will not glow in a reduced-voltage current-limited circuit = the gp harness

You mentioned an eternal pump DTC?

[arveetek]

Pulling the ECT connector results in PCM thinking it's -40degF outside - you get max glow time, full advance and more fuel - if that heals hard-start, you got glow problems or IP problems or fuel supply problems - or, even worse, all the above - could even be worser, tho: low compression



I initially did my mod to solve an intermittant hot-start problem. This helped a bunch, but I believe the ultimate root cause of the problem was a failing FSD. After replacing the FSD, I never had another hard start or stalling issue. I just left the temp-switch mod in place, since it starts so easy that way.

Casey

[gmctd]

That modification won't hurt anything - I've suggested it many times, but with an added series resistor which is shorted by the NC contacts - engage the relay, contacts open, resistance is added to ECT sensor, -40deg scam on the PCM - don't like opening live circuits while PCM is powered up - good thought BTW on the alternator permissive hookup

rbr really needs to troubleshoot those three areas B4 winter sets in, tho - I 'magine it's a hard row to hoe, trying to repair and bleed the fuel system or get the gp's out in 0deg weather