Dumb Question - and Longtime Goose Chase

[Emmo]

Hi all (I love this forum but post rarely)

Just want to confirm, a dumb question. Does the distributor take the place of a crankshaft position sensor? On our trucks no such sensor exists, is that a correct statement.

Been chasing an issue for several years whereby the truck runs terrible on really hot days, it'll start no problem but just runs bad. In the winter and mild summer days no problem just like new and super strong. Otherwise on hot summer days, the boost cuts at 0 along with the fuel pump supply, it wants to backfire and surges, and the A/C clutch stops resulting in only hot air circulating. Have to feather the throttle pedal to build speed and limp home to wait for cooler temps. I've chased this over several years and replaced to date :

Knock sensor
Oil Pressure Sensor
Vacuum Lines
Radiator
Water Pump
New Johnson Cooling IC pump (hot wired)
Brake Booster
Fan Clutch
Cleaned Fuel Injectors
Replace to AFP regulator (pressure confirmed with gauge to 42psig w vacuum line off)
IAC changed
Engine Temperature Sending Unit replaced
Ign Coil
Distributor (confirm #1 position manually despite timing light problems)
Stock Harmonic Balancer is ok (no slippage I've confirmed)
Ignition Modules with grease (tried two have extra now)
Cap Rotor Wires Plugs
Boost Solenoid
New Boost Gauges and Temp Gauge in cab all read within norm temp
Stock Thermostat and Hoses
Heater Core (dumped coolant on passenger floor)
Gel Battery Brand New
Alternator
Checked wiring harness several times from ECU and around firewall (no frayed wires)
Starter (Mini Style now)
Purple wire is okay
edit: New Walbro fuel pump and filter 2 years ago (problem predates/postdates pump and filter install)


Everything is bone stock except for running no mufflers and 3" pipe, and rerouted IC lines through front right fender. Stock chip etc.

I'm now down to replacement of Map Sensor, complete stock ECU, Prom, wiring harness, and maybe a Crank Sensor (if it exists) ? What else could be temperature dependent?

I've got DataMaster on little laptop and need to read a little more on how to properly save files, I can record live but havent figured out how to save to post here.

Thanks for any advice or notes to my rambling above...:tup:

Love the info here! Pete

 

[JSM]

Re: Dumb Question - and Longtime Goose Chase

Crank angle sensor are only needed when you have several coils, aka coil on plug systems. Typically newer cars all run this setup, our syty's are very old technology and run a true distributor that sends spark to the right cylinder via mechanical method (cap and rotor) using 1 coil.

There is a module under the cap that often goes bad, might try one of those first. (it only controls amount of timing not which cylinder to fire)

 

[BoostedSUV]

Re: Dumb Question - and Longtime Goose Chase

our trucks do not have crank sensors but that's a very weird issue. Have you confirmed ignition timing is set to zero (with the brown wire disconnected)?

 

[Emmo]

Re: Dumb Question - and Longtime Goose Chase

Yep, top dead center #1 is confirmed with brown wire disconnected. I couldn't get the timing to set steady with the timing light as it was slightly jumpy. Hence I confirmed top dead center with a piston stop from Summit and carefully hand turned the new distributor until #1 spark plug fired (as I could see by my eyeball and plug grounded), then locked distributor nut down. Confirmation that timing is at zero, mechanically. The harmonic balancer is basically okay, hasn't slipped and I marked the marks with paint marker...it was real close to set with the timing light but slightly jumpy so I did it mechanically as helped by DaveP last summer :tup:

Yep, it's a weird situation...I'm still on the hunt :banghead:

Thanks guys!!!

 

[CC801]

Re: Dumb Question - and Longtime Goose Chase

So let me get this straight the boost goes to zero and the fuel pressure as well? And only when hot outside? Sounds like a definite fuel problem...could be a pump if its temp dependent.

 

[Emmo]

Re: Dumb Question - and Longtime Goose Chase

Ahh...I forgot to mention...pulled the bed and replaced the fuel pump 2 summers ago with a Walbro from RPM...stock injectors...and 2 year old fuel filter. Issue predates fuel pump and filter swap.

Keep in mind this is only when really hot outside like 95deg plus days. If it's about 90 degs outside it takes about 15 minutes of driving around , normal pace, and then it acts up. Any temp below say 80deg runs perfect no problems...

Will update original to include swapped fuel pump....good reply CC801....I'm open to all ideas.

Could there be anything whatsoever related to the transmission? I don;t know all the logic of the ECU so just guessing here.

Next time it acts up will attempt a video of dash boost /temp / oil pressure / sounds etc and post

Thanks again all !

 

[Don W.]

Re: Dumb Question - and Longtime Goose Chase

Random thoughts: Any codes? Do you have a data logger, IE Datamaster? I'm thinking maybe a faulty intake air temp sensor. And/or water temp sending false data to ECM? High temp breakdown of ign module??

 

[berzerker]

Re: Dumb Question - and Longtime Goose Chase

did you change out the fuel pump wiring harness inside the tank ? my guess is the connectors are shot and build resistance as everything in the tank get warm . does the truck have the stock catylitic convertor on it ? this could be the issue also .

 

[Emmo]

Re: Dumb Question - and Longtime Goose Chase

Couple of replies, First for Don W.

To - "Random thoughts: Any codes? Do you have a data logger, IE Datamaster? I'm thinking maybe a faulty intake air temp sensor. And/or water temp sending false data to ECM? High temp breakdown of ign module??" -

I did have a 51 code two days ago no other codes. Looked it up and says:
"Check that all pins are fully inserted in the socket and that PROM is properly seated. If OK, replace PROM, clear memory, and recheck.
If Code 51 reappears, replace ECM."

...I pulled ECU out carefully (Ive done before), inspected the wires, carefully put it back...all wiring looks good. DID NOT REPLACE PROM....so there might be something there and the fact that the ECM is original with stock chip. I read something on Napa website that -

G.M. Electronic Control Computers with surface mount technology.
Original part numbers are:16156647, 1227165, 1227303, 1227727,
1227730,1227748, 1227749, 1228253, 1228321, 1228547, 1228706,
and 16149396.
Engine misfire, hesitation, and intermittent check engine light
and stalling.
The original conformal coating applied by G.M. swelled, causing
movement of the electronic components and cracking of critical
solder joints.
In 1994, a new process was introduced into production by NAPA. The
original conformal coating is removed, then the components on the
printed circuit board are resoldered and tested. Finally, a new formula
conformal coating is applied to seal the circuit board to complete
the process.
NAPA Electronic Control

...So I cleared the 51 code two days ago. All ran well in garage. Then yesterday took out in the morning to play a little golf, about 70 deg here in Atlanta, no problem ran fine. Then at about noon it was 88 degs and time to go home from the round....within 2 min of driving truck acts up and have to put on flashers and feather the throttle home on I-20 in the right lane. So problem still there. I then drove last night (cool) all ran well and again this morning (cool) .... all ran good. I saw this post and I rechecked the codes...and lo and behold a "51" pops up again.

I've replaced the IAT sensor two years ago. I replaced the temperature sending unit for engine coolant temp that goes to the ECU (top of the block by hose) also two years ago. The one lower on the block is running to a newer gauge inside the cab...all looks fine. Temperatures all look good at all outside conditions...I believe the engine is cooled just right.

The ignition module was replaced last summer and then the distributor was also swapped. Have extra modules but believe all three are fine.

I confirmed that the MAPP sensor is indeed stock at 2 bar and original from 1991. Don't know if I can even test that, maybe just swap it?

I'll attempt to do a datamaster record today.

Thanks Don! Reply to berzerker next post.

 

[Emmo]

Re: Dumb Question - and Longtime Goose Chase

Reply to berzerker,

"did you change out the fuel pump wiring harness inside the tank ? my guess is the connectors are shot and build resistance as everything in the tank get warm . does the truck have the stock catylitic convertor on it ? this could be the issue also ."

Ahhh.... I did not change out the fuel pump wiring harness!...just cleaned up and replaced pump and filter. There was also little union connector (black with gold bumps) allows fuel line to couple inside the tank. I used what was in the kit from RPM and that little union connector did not go back in. It may be a kind of bellows. Photo below...I left it out and dont think it matters, my problem was there before/after pump changeout. And I did throw it away I remember now, can get a new one if needed. Luckily I took a lot of photos during the Summer 2010 restoration,

Now as for the wires...to be certain. Are these the wires in question, see image below. Would I just swap the connector with new and splice the wires in further upstream? There are no wires inside the tank that I remember, just connectors. All looked visual okay inside the gas tank Summer 2010 when I did the swap.

Now as for the catalytic converter....YES, it is NOT STOCK...it is a HIGH flow converter with 3" inlet and exit...no mufflers either. This current converter was to replace the second converter I've had since new ( first two converters got plugged ). Now current converter has been on the truck maybe 6 years or so. I am lucky to pass emissions every year around October and have to wait until a very cool 60 deg day to go, otherwise I fail. O2 sensor is fairly new at 4 years old. Once 25 years hits the truck wont need emissions :tup:

In the beginning and today with the high flow converter if it is cold outside, around 40 deg, the truck is capable of overboosting and cutting the fuel. I've adjusted the stock wastegate linkage as best as possible to remedy this. Typically it is a minor issue and I never overboost in the summer. In the winter, I'm just careful and really have to hammer the throttle to overboost and cut the fuel.

I've pondered putting the muffler back on to help backflow pressure...but dont know or think this contributes to my summer time problem. Let me know what you think, I'm okay with going back to mufflers (my old age I like quiet trucks now :sleepy: )

Thanks bezerker, curious what you think I'm definitely okay with replacing the wires to the tank and see what happens.

All good stuff guys, thanks a bunch!

 

[Don W.]

Re: Dumb Question - and Longtime Goose Chase

Interesting. Thanks for the detailed answer. Do you have a spare coil? Wouldn't be the first time that one fails with high temps. Also check the connectors at the coil and dist. There has been instances where that connector wire (coil to dist) was bad.

 

[Icarus-54]

Re: Dumb Question - and Longtime Goose Chase

The little thing with gold bumps is called a pulsator,it take the shock out of the fuel line.Some trucks will get a knock count with out this.Is the any chance you have your inter cooler lines mixed up and maybe drawing from the top port instead of the bottom?

 

[Emmo]

Re: Dumb Question - and Longtime Goose Chase

Hi!

Reply Don W. - I dont have an extra coil...tossed the old one and have a 1 year old MSD...should be okay I'm hoping. I'll go double check the wire from the coil to the distributor today.

Reply Icarus-54 - I'll double the coolant line routing to be sure all is okay.

Side note - I think I got the datamaster program running again here and found some old files ....so I will clear the 51 code and attempt to log a little this am while it's cool. Then try a hot afternoon run. Then try and post file ...will keep you all posted!

 

[Icarus-54]

Re: Dumb Question - and Longtime Goose Chase

Get rid off the msd coil,I've had 2 brand new ones that were no good.

 

[Don W.]

Re: Dumb Question - and Longtime Goose Chase

X2 on the coil. I had one bad out of the box. My current one is on the bench.

 

[Emmo]

Re: Dumb Question - and Longtime Goose Chase

Hi, couple of updates and yes got the datamaster working after some readings this morning and last night.


To confirm Icarus-54 - The IC lines are fine. Coolant flowing as it should, pump pumping and hotwired on with ignition. Data files showing IAC temps of 140deg to 160 deg.

Don W, I checked the ignition coil wire.....the white and pink all look good. Now there is a spliced wire in there for a Viper remote start. Picture below. It's not the prettiest but I think the connection is good. I black taped it up again after the picture and secured it. IF, this is a major concern I could cut it out and redo the connector. Thoughts welcome but think I'm okay. When it's cold the coil and the engine "seem" to be running fine...I have not yet thrown out idea completely of replacing coil again. Will attempt datamaster files in next post below, and hopefully it'll help in the mystery...

 

[Emmo]

Re: Dumb Question - and Longtime Goose Chase

Okay, hopefully this can help too...was able to successfully get a couple of "cold" ambient temperature data files this morning. Initially I was having problems with datamaster cable saying "No PCM Sync, Recycling" and pause data recording until I read that I had to adjust the setting "ALDL Timing Link" to 190 instead of default to get full data without jumps in time.

Hence, I believe I have my first ever datamaster files posted below. The truck is running fine, the AC was on, the air temperature this am was about 70 deg to 77 deg when collecting data. No problems and truck seemed to be good. Files below.

Run 1 - Startup and light running around town - 4 minutes
http://www.mediafire.com/?bpjnah1da2cz8nn

Run 2 - Couple of strong runs with boost - 2 minutes
http://www.mediafire.com/?ner1d42c6h3onhi

Run 3 - Longer run around town with fast highway speed - 11.5 minutes
http://www.mediafire.com/?72nb73mp253rreo


Next I will wait for a hot afternoon mid 90s, hopefully today, and get some issues and data log that into the next post.

Thanks so much all for the interest and help! Pete :tup:

 

[Emmo]

Re: Dumb Question - and Longtime Goose Chase

Get rid off the msd coil,I've had 2 brand new ones that were no good.

I just read this....will do. No way to test it I suppose? Figure I'll get a new one (other than MSD) from Napa or AutoZone or Advanced...will keep you posted!

 

[vinnieTy]

Re: Dumb Question - and Longtime Goose Chase

Just some ideas....when you stated the code 51 came up was this when the truck started to run like crap or before it did.
Why don't you try this Disconnect battery and wait 15 minutes (When the truck starts running like crap). After 15 minutes reconnect the battery and try it. If it doesn't happen then more a ECM or electrical connector like a temp sensor issue. Of course just my opinion.

 

[Static]

Re: Dumb Question - and Longtime Goose Chase

I think theres issues with your IC. For an 80 degree day your seeing 160 ish IAT. This seems very high to me. How many miles on the truck? I would inspect the lower exchanger internally, check for kinked hose, do the hard line bypass if you havent already, refill the system and make sure no air is trapped.