Starting Trouble

[gogmorgo]

Open loop is essentially a "warm up" mode. It mostly just runs a bit rich, like the choke on a carb'ed engine. I would think 175°F would be enough to kick it into closed loop, but I'm just guessing on that. 

[kryptronic]

Not sure on Renix, but this is true for HO:

 

The system will go into closed loop at 195 degrees.  All signs point to a sensor issue as everything runs great in open loop.  Culprits are likely the crankshaft position sensor or the camshaft position sensor.

[Hudy]

Okay, MT2500 readings:

 

RPM: Constantly reading between 800-3000, even with the truck off

 

O2: Jumping from 0.5 to 4.98

 

INJ (mS): Jumping from 18.1 to 0

 

Loop status: Jumps from open to closed every 3 seconds

 

Exhaust: Rich / Lean jump

 

ST fuel trim: 162/128 jump 

LT Fuel trim: 125

MAP sensor (V): 0.7 to 4.6 range, goes up and down

 

MAP sensor (kPa): 25-94 range

 

MAN VAC (kPa): ranges from 2 to 74

 

BARO pressure: 99

 

TPS: .66 to 2.5 (at idle

 

throttle %: 13 to 50 (at idle)

 

throttle sw: partial

 

fuel sync: +\-

 

coolant: 88

 

Charge temp: 43

 

spark adv: 0-26 range

 

knock: 0-53 range 

 

egr: off

 

 

 

 

 

 

 

[Ωhm]

Need to check powers and grounds to ECU. Your readings seem to be all over the place.

 

Check for voltage (connect one lead at battery negative):
D1-5:  B+ at all times
D2-4:  B+ with KEY ON/START/ENGINE RUNNING
D1-6:  B+ for 2-3 seconds when KEY is turned ON or B+ at all times with ENGINE RUNNING

 

Check for path to ground (connect one lead at battery negative) KEY OFF:
D1-3:  0 ohms
D2-8:  0 ohms
 

[JMO413]

Do you by chance have the scanner on trouble shooter or something like that. I only ask beacuse mine read like that after I was playing around with it. I just started over and it all worked correctly then. Add the vehicle like your starting from scratch.

[Hudy]

13 minutes ago, Ωhm said:

Need to check powers and grounds to ECU. Your readings seem to be all over the place.

 

Check for voltage (connect one lead at battery negative):
D1-5:  B+ at all times
D2-4:  B+ with KEY ON/START/ENGINE RUNNING
D1-6:  B+ for 2-3 seconds when KEY is turned ON or B+ at all times with ENGINE RUNNING

 

Check for path to ground (connect one lead at battery negative) KEY OFF:
D1-3:  0 ohms
D2-8:  0 ohms
 

D1-5: 12.95

D2-4: Key on: 11.9 - 12.1

start: 11.3

running: 13.8 - 14.1

 

D1-6 running: 14.5

 

D1-3 OHM: 0.5

D2-8 OHM: 0.6

 

 

 

 

 

[Hudy]

5 minutes ago, JMO413 said:

Do you by chance have the scanner on trouble shooter or something like that. I only ask beacuse mine read like that after I was playing around with it. I just started over and it all worked correctly then. Add the vehicle like your starting from scratch.

These readings are in live data on the MT2500, with a fresh vehicle entry.

[JMO413]

I would agree with Ohm then.

[Ωhm]

Values you posted are all good and normal readings. I would now suspect the ECU itself. Let others chime in, maybe I'm missing something.

[Hudy]

2 hours ago, Ωhm said:

Values you posted are all good and normal readings. I would now suspect the ECU itself. Let others chime in, maybe I'm missing something.

 

I suspect the same. Thanks for all of your help!

[coolwind57]

On 10/1/2019 at 7:44 PM, Hudy said:

Coolwind, I'm excited to see how that might help. 

Well, a new coil isn't the solution.  Same ol' issue.  Sorry man.  

 

On 10/1/2019 at 7:44 PM, Hudy said:

could it be that the computer doesn't know what to do, or perhaps grossly miscalculates the values when it sees an open loop reading from the CTS? 

Keep us updated por favor.  I just heard a comment after starting last night as I left work, "Good Lord man, is your truck running rich?"    

[coolwind57]

Where do you get with your IAT (aka Manifold air temperature sensor and by other names)?  Looks like you found some issues but I didn't see a followup. 

 

I'm reading that its resistance is read by the ECU to help determine fuel/air mixture.  If it doesn't do its job and is an open circuit (non continuity), it causes the ECU to enrich the fuel/air mixture on a hot engine because it thinks the engine is cold.  Sounds like it can be related to our issues.  Apparently, same goes for the CTS (coolant temperature sensor) located on the driver's side of the block.  http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

 

I'm going to go check mine along with my CTS when I get some time.

 

 

[Warren Mohler]

I had similar problem last spring started fine cold hot engine cranked for a long time then started when I would go wide open throttle I found fuel pressure regulator leaking gas into vac. hose causing flood condition $33.00 for regulator from Rock Auto fixed it right up. Good luck

[Hudy]

5 hours ago, coolwind57 said:

Where do you get with your IAT (aka Manifold air temperature sensor and by other names)?  Looks like you found some issues but I didn't see a followup. 

 

I'm reading that its resistance is read by the ECU to help determine fuel/air mixture.  If it doesn't do its job and is an open circuit (non continuity), it causes the ECU to enrich the fuel/air mixture on a hot engine because it thinks the engine is cold.  Sounds like it can be related to our issues.  Apparently, same goes for the CTS (coolant temperature sensor) located on the driver's side of the block.  http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

 

I'm going to go check mine along with my CTS when I get some time.

 

 

 

I used a resistance chart to determine whether the MAT (manifold air temp) Sensor was functioning properly. I had a spare, so I tested that one first. Used heat gun to heat the unit and a thermometer gun to read the temp, and compared that to the resistance shown on the meter. The spare tested good, so I installed it. I took the existing (old) sensor out, and tested that one, which tested BAD; the values it showed were false COLD.

 

I also have a spare CTS, which I tested using the same method. I haven't installed that one yet.

 

I did receive a new ECU in the mail today. I'll install that tomorrow and report back with the findings. 

 

Chart attached.

 

38 minutes ago, Warren Mohler said:

I had similar problem last spring started fine cold hot engine cranked for a long time then started when I would go wide open throttle I found fuel pressure regulator leaking gas into vac. hose causing flood condition $33.00 for regulator from Rock Auto fixed it right up. Good luck

 

I could see this happening in your case, but in mine I know i'm holding fuel pressure. 

[Warren Mohler]

Hey only takes a second to pull the hose off and check for fuel mine had good psi running never checked to see how long it held  just know what fixed problem

[coolwind57]

10 hours ago, Warren Mohler said:

Hey only takes a second to pull the hose off and check for fuel mine had good psi running never checked to see how long it held  just know what fixed problem

Great stuff.  I'll run out and check mine later today.  Thanks for the tip.  Would be wonderful to finally resolve this dumb issue.  

[Hudy]

New ECU install, not sure yet on repair status. Turns out the Snapon tool I had was faulty (reading the same even with the ECU unplugged).

 

Located a new tool quickly, readings attached.

[Ωhm]

STFT (45) shows engine running RICH, engine is in closed loop, so ECU is within its range of authority. That means good. Look into Throttle(%)/Throttle(v), readings seem low. Faulty ECU or faulty TESTER, man tough call there.

[Hudy]

40 minutes ago, Ωhm said:

STFT (45) shows engine running RICH, engine is in closed loop, so ECU is within its range of authority. That means good. Look into Throttle(%)/Throttle(v), readings seem low. Faulty ECU or faulty TESTER, man tough call there.

 

Yeah... although I don't regret buying the ECU. I'll probably leave the reman installed and put the old one in the basement as a spare. Who knows how long these units will be available for.

 

Anyway: The issue persists with the hot starting.

 

I had adjusted the TPS using cruiser's guide, and actually rechecked the spec a few days ago and it was where it needed to be. Is there more to check here?

 

With the coolant temp at 199*, shouldn't the system be in OPEN loop? 

 

[Ωhm]

When O2S heats up (O2 Heater) and starts rapidly switching (RICH/LEAN), ECU should go into CLOSED LOOP.

Not sure how TESTER calculates Throttle(%) or TPS(V), could be normal readings, but the TESTER should display only what the ECU sees. You did recheck values with a DVOM?

 

Does the parameter for EXHAUST switch for RICH to LEAN quickly?
 

[Hudy]

14 minutes ago, Ωhm said:

When O2S heats up (O2 Heater) and starts rapidly switching (RICH/LEAN), ECU should go into CLOSED LOOP.

Not sure how TESTER calculates Throttle(%) or TPS(V), could be normal readings, but the TESTER should display only what the ECU sees. You did recheck values with a DVOM?

 

Does the parameter for EXHAUST switch for RICH to LEAN quickly?
 

Yes, using Cruisers guide checked TPS valued using a mulimeter.

 

Yes, exhaust goes from rich to lean quickly.

 

I am skeptical on the CTS still. I’ll install that tomorrow. 
 

Unfortunately I only had the tool for a snapshot and couldn’t keep it to monitor data as the motor heats up. 

[Ωhm]

Not going to tell you not to swap out the CTS(ECT) sensor, but if engine was at normal operating temperature, 199° seems like a valid reading.

Too bad on no TESTER being around. Would've liked watching FT for awhile. Your STFT reading shows INJ PW (4.6mS) going LEAN. If this is true, suggest the following:
Fuel rail pressure could be HIGH. Check vacuum hose from manifold to fuel pressure regulator. Connect fuel pressure gauge. With engine running look for 31psi at idle and 39psi with vacuum hose removed/plugged and engine running. Make sure fuel rail hold pressure for at least 30 minutes (leaky injector(s)).
 

[Ωhm]

On 9/20/2019 at 7:53 AM, Hudy said:

1. I have great fuel pressure and it holds fuel pressure. 

Just re-read your first post.

[Hudy]

1 hour ago, Ωhm said:

Not going to tell you not to swap out the CTS(ECT) sensor, but if engine was at normal operating temperature, 199° seems like a valid reading.

Too bad on no TESTER being around. Would've liked watching FT for awhile. Your STFT reading shows INJ PW (4.6mS) going LEAN. If this is true, suggest the following:
Fuel rail pressure could be HIGH. Check vacuum hose from manifold to fuel pressure regulator. Connect fuel pressure gauge. With engine running look for 31psi at idle and 39psi with vacuum hose removed/plugged and engine running. Make sure fuel rail hold pressure for at least 30 minutes (leaky injector(s)).
 

Well, looks like my fuel pressure regulator is leaking fuel into the vacuum system. Pulled the vacuum line off to discover fuel dripping from the line. 

 

Strange, because I am holding fuel pressure.
 

 

 

[Warren Mohler]

don't get lost in resistance charts and all that stuff I have been working on renix systems ever since they hit the market this is about the most basic fuel injection out there heating up sensors and taking ohm readings is fun to do but very seldom solves a problem fly by the seat of your pants. like Cruiser says check everything all electrical  connections and hoses bumper to bumper to get an overall big picture of conditions before getting scan tools and multimeters out. Rock Auto had the cheapest regulator I could find its a little tricky getting both nuts and lock washers back on with fuel rail on I tossed washers and used locktite anyways I hope this fixes your problem. Lets keep them running.