1995 454 flooding

junkfxr · August 1, 2020

Hello all, new to the forum but not new to turning wrenches. I have a problem that's got me stumped and aggravated to death with my truck. It's a 1995 K2500HD, 7.4 tbi, NV4500 with 254k miles. pulled out of the driveway yesterday and it fell on it's face and was trying to die. Got it back to the house and it's running super rich, blowing fuel out of the pipe. It will run above 2500 rpm but blowing black smoke and dies at anything lower. The SES light wasn't on and there were no codes logged. Checked the fuel pressure and it's 32 psi, within spec. Replaced the ignition coil and throttle position sensor yesterday afternoon and no change. Replaced the IAC and MAP sensor this morning while the engine was cold. It started and ran fine until the temperature started to come up and it started doing the same thing, dumping fuel. The SES light came on and logged three codes,15, 35 and 54. This is an OBD1 system. I'm leaning towards the egr valve and / or temperature sending unit. There are two temperature senders on this engine, one in each head. Does anyone know which one is used for the ecm? Any thoughts on the whole thing? Any help is GREATLY appreciated. Thanks in advance.

Kineticarts · August 1, 2020

With 1/4 million miles on it I'd think something is worn or broken and I'd check the engine reference grounds. I found a wire broken within the intact insulation where it was attached to the block once. It made the PCM try to make the engine do funny things and set all sorts of funny codes. Just the repeated flexing between the block and wiring harness was enough to break the ground wire. Does the cone from the injectores look even all the way around and between the two? Could be the wear just reached the point where the programming couldn't compensate for it any longer.

grampadirt · August 4, 2020

There are three temp sensors....the one one the pass, head is actually a switch which will close at approx. 220*(I tested mine in a pan of boiling water with a thermometer) and turn the aux, fan on.The one in the drivers side head runs the temp gauge,the one under the thermostat housing sends a signal to the PCM(this one has a direct effect on how fuel is delivered to the engine).Remove and clean the EGR valve of any carbon build up on the valve and in the intake manifold(I use a vacuum cleaner as I scrape and clean).Check the TPS to make sure it sends a smooth signal to the PCM,a DMM will work here.Also,the ICMs are a known weak point on these distributors,check that.one more thing,be sure to check the timing with the connector(under the glove box)disconnected,it should be 4* BTDC.You can try a reset precedure on the IAC,might help.

Do yourself a favor and subscribe to alldatadiy.com,I've subscribed for years and it has helped me immensely.Good Luck.

junkfxr · August 7, 2020

On 8/4/2020 at 1:46 AM, grampadirt said:

There are three temp sensors....the one one the pass, head is actually a switch which will close at approx. 220*(I tested mine in a pan of boiling water with a thermometer) and turn the aux, fan on.The one in the drivers side head runs the temp gauge,the one under the thermostat housing sends a signal to the PCM(this one has a direct effect on how fuel is delivered to the engine).Remove and clean the EGR valve of any carbon build up on the valve and in the intake manifold(I use a vacuum cleaner as I scrape and clean).Check the TPS to make sure it sends a smooth signal to the PCM,a DMM will work here.Also,the ICMs are a known weak point on these distributors,check that.one more thing,be sure to check the timing with the connector(under the glove box)disconnected,it should be 4* BTDC.You can try a reset precedure on the IAC,might help.

Do yourself a favor and subscribe to alldatadiy.com,I've subscribed for years and it has helped me immensely.Good Luck.

It was the temperature sensor in the front of the intake. It was buried under a gob of wires and I completely overlooked that one. it originally wasn't throwing any codes at all, just flooding itself. Thank you for the information.

grampadirt · August 7, 2020

10 hours ago, junkfxr said:

It was the temperature sensor in the front of the intake. It was buried under a gob of wires and I completely overlooked that one. it originally wasn't throwing any codes at all, just flooding itself. Thank you for the information.

You're Welcome,glad I could help.