papasmurf

I did not...had rented it from o'reilly's the other day and had already returned it.

papasmurf

I ordered a fuel pressure regulator this evening...will be here monday. I am still not convinced what the problem is but figured I would have it on hand if needed and can return it if I get it fixed beforehand. Just for kicks I swapped two other computers I had on hand into the car this evening. Neither ultimately seemed to make the car run any better so I went back to the original computer. I measured the DME temp sensor at the DME computer plug (pins 13 & 17 I think?) and came up with 1.03 ohms at whatever ambient temperature (~85?) was at. I did not get to warm up the car or test the sensor externally as indicated but may try again monday. After putting the original computer back in the car I got it started after a few tries but it took quite a while of barely idling before the idle rose to normal specs again. I let the car sit for 10 minutes or so and tried again and after about 6 attempts of cranking, gave up as it does seem the problem is getting worse as it is more often just turning over without firing now rather than sputtering to life pretty quickly like it did before.

T&T Racing

Consult Clark's Garage for help.
Here is the test procedure from Clarks Garage for DME Temp Sensor.
DME Temperature Sensor Testing

Tools


Multimeter
Test Leads
Procedure


Turn the ignition switch OFF.
Disconnect the DME computer electrical connector.
Connect an ohmmeter between terminal 13 on the disconnected DME plug and ground.
Check for the following resistances:
DME Temperature Sensor Resistances
15-30 °C (59-86 °F)
At 59 °F approximately 3.3 k-ohms
At 86 °F approximately 1.46 k-ohms
NOTE
The next part of the DME temperature sensor testing assumes that the temperature gauge on the dash is working properly.

Connect the DME plug connector.
Start the car and run until the temperature gauge on the dash indicates approximately 80 °C (see dash temperature gauge section). If you suspect that the dash gauge is not working properly, you can check the surface temperature on the block near the DME temperature sensor.
Turn the engine OFF.
Disconnect the DME computer plug and connect ohmmeter as described in Step 3.
Turn the ignition switch back ON (Do Not Attempt to Start Car) and check dash indication is still reading 80 °C. Alternatively, check the surface temperature on the block near the DME temperature sensor. Compare resistance to the value in the table below.
DME Temperature Sensor Resistances
80 °C (176 °F)
280-360 ohms
If the resistances don't meet the tolerances listed, the DME Temperature sensor should be replaced. If the resistances indicate higher than the specs, it will cause a richer mixture. Lower resistances than the specs will result in a lean mixture.

walfreyydo

DME temp sensors are like $15 so worth changing

papasmurf

Put in the new fuel pressure regulator last night but didn't get to test it as two of the fuel injector o-rings split putting them back in the fuel rail. Got the new o-rings today and got it running but it is the same as before and like I said before seems to be getting worse in the number of starting attempts it takes before the car actually runs properly. I pulled the AFM assembly and swapped it quickly with another one I had that was of unknown/suspect quality and had no luck there. It was at that time I realized while messing with the throttle that I could not here the click of the TPS right off idle. I checked the sensor through the DME per clarks garage and got nothing at idle or WOT and again got the same results at the TPS plug when I pulled the throttle body. I adjusted the TPS and got it positioned where it would click just off idle like it should and the idle readings were there but I could not get any WOT readings. I had a spare throttle body/TPS that according to the multimeter checked out okay so I swapped the two sensors and put the car back together quickly. It still seemed to take too much time to fire up and ran rather poorly and a bit erratic at times. The car seems to stumble some when revving and sometimes seems like it wants to die at idle now. I did several back to back starts and it never fires off immediately like it has in the past. I will admit the fuel light is now on and the car is almost totally out of gas now but I don't think fuel starvation is my issue as it never died completely yet. I just ran out of time tonite to work on it anymore...will put some fuel in it and do the DME temp sensor test next time I am able. I pulled the computer plug one last time before calling it quits and checked the "new" TPS sensor through the harness again...idle readings were good...took a few tries to get any reading at WOT but that could of been because I was trying to open the throttle, and hold one test lead wire grounded all at the same time. The car ran poorly enough I may put the old TPS on it and just see what it does again with the idle click set again properly. It's frustrating as the car has started and ran really well over the past year since I put it back together always starting with little trouble and very little cranking needed but now it seems to get worse each time I mess with it.

T&T Racing

0n previous post, you stated
"The injectors were rebuilt/cleaned/flow tested when I bought the car. I pulled them myself and did the battery/carb cleaner test last year when I was diagnosing the fuel tank problem. I am not saying they couldn't have gone bad or are not gummed up now but the car has very little run time since then and seems to run fine once it can get past the sputtering idle."

But what was the fuel tank problem????

Stumbling is lack of fuel or too much air. Do you know if one or more injectors are partially plugged? You stated it takes several tries to start the engine which indicates the fuel injectors are not delivering sufficient fuel for a start condition, ie issues with the fuel injectors. Must rule out fuel injectors even though clean and tested previously.


Check fuel flow from each fuel injector by removing fuel rail and placing each injector into a identical volume jar
Crank engine for several seconds. Observe fuel volume in each jar. If not all the same, have fuel injectors tested and cleaned. SouthBay Fuel Injector Service can do an excellent job.

papasmurf

The fuel tank was shedding rust clogging the fuel system. The tank was pulled, split apart, cleaned, and resealed with red kote.The fuel pump was replaced, along with the fuel filter, and the tank screen was cleaned.

walfreyydo

Again, recommend replacing the DME temp sensor before doing anything else. They are available on Amazon for $15. Your sensor might be telling the DME that the engine is warm and not richening the mixture enough to start the car or to keep it running smooth. Once your engine starts to warm up a bit from multiple starting attempts, it begins to run better. The symptoms seem to fit this being a potential cause.

Also second what T&T said, running your injectors into cups to measure fuel flow. You might also want to check and clean your grounds, particularly the ones on the bellhousing and the power connections to your starter. I had an intermittent rough idle problem recently that ended up being those connections.

In terms of the TPS you can carefully open them and clean the contacts inside the unit. They are binary (951 units are potentiometers) so they basically make contact and break contact. Something to try.

papasmurf

I installed a new Bosch DME temp sensor (to replace the URO part) as I never could get reliable readings while doing the diagnostics on the old part as I really can't warm the car enough to do the various tests. I don't think the old part was necessarily bad but it was easier to replace at this point then waste more time trying to test it. Unfortunately that did not seem to fix the problem. I installed the parts yesterday and on about the third starting attempt it started normally for about 2 seconds max before dying...no stumbling, just dead. The car was really low on gas so I did not get to mess with it again till today after adding 5 gallons of fresh fuel (completely drained the tank of any old fuel prior) but again the first crank it started easily for about 2 seconds before dying instantly. Subsequent attempts at starting it would catch in that I was not just cranking aimlessly without ignition of some sort but it would die instantly and the tach would never show more than 2-300 rpms. I did the external tests on the AFM per clarks garage and it all seemed to pass. I got 10 something volts at the plug from the DME as input voltage and the max output voltage from the AFM when the barn door was at WOT was somewhere in the 8's. I pulled the reference sensor plugs to check them and got some readings but not necessarily the right readings and I need to do this again and make sure of which one speed/ref I am actually testing. The one closest to the back of the car is slightly loose when I wiggle it on top of the bell housing in that it can be rotated maybe 2 degrees I am guessing. The bolt that holds it down seems to be tight though. There is also some ferrous material buildup I can see on them so I will probably pull them, and clean them just to be sure. I still need to check the injectors flow and I guess check for spark at this point. I think the injectors at least to some extent are good as you can certainly smell fuel vapor from the attempted starts. Lastly, I installed the original TPS again as the car previously ran/drove with this sensor but I still have not gotten a WOT signal when doing the diagnostics on this part.

walfreyydo

What are the fuel pressure readings once it dies? Does it still show 37psi? With the car dying right away Im wondering if fuel flow is becoming obstructed (clogged filter). You mentioned earlier that you had a lot of debris in the fuel tank - I assume you replaced the tank strainer and fuel filter after cleaning/sealing the tank?

papasmurf

The tank strainer was cleaned when I resealed the tank...fuel filter has been swapped twice as well. I will have to check the fuel pressure again....that was back when it was running.

papasmurf

I tried to get some measurements on the fuel pressure readings today but oreilly's had already loaned out the fuel pressure setup I borrowed last time...will probably just order my own gauge online now. I have fuel at the rail as I flushed it out the front but of course had no way of actually measuring the pressure. I went ahead and checked out the speed/reference sensors through the DME plug just to rule that out and they measured okay. I pulled them both just to clean any metallic filings off the ends as I could see some buildup around the edges but they were mostly clean. I also checked the coil for the appropriate ohm and voltage specs and it mesaured good as well. I tried starting the car once or twice after each item was tested/measured with no luck until the last item (coil) and it fired off immediately and ran normal for about 3-4 seconds before dying and would not start again after two more attempts. I will probably pull the fuel rail and check the injectors for flow if I have time tonite and check fuel pressure as soon as I am able to again.

papasmurf

I tested the fuel system again today and with the pump priming the rail it measured about 37 psi again. I turned off the key and it gradually would fall to the low 20's after a few minutes. The setup I rented of course does not have the adapter for the 944 rail so I had to improvise with some hose clamps and tubing and even with it cinched tight there was a very minor fuel drip so I did not do the full 20 minute leakdown test. I was unable to test it running as the car would not start at the time and had to return it. I checked the plugs for spark, and pulled the fuel rail apart to measure and compare the flow of the injectors. They all were firing evenly and with a good spray pattern it seemed. I pulled the distributor cap to take a look at it and the rotor and it looked pretty normal and spotless...cleaned one small area but I think it was fine. Like before, I tried starting the car briefly after each system was checked or tested...no luck until I put the distributor back on and it ran briefly before dying. It would seem to run fine for about 5-10 seconds before abruptly dying and did this 4 or 5 times. I took some videos of the subsequent attempts to start the car and it was at least trying to run when it wasn't before but was having a really hard time getting to idle before dying. This went on for probably 8 more attempts at least where it would struggle for 5-10 seconds before dying again. On the second video it was running with some sort of consistency though if you revved the engine and let off the gas the idle would fall pretty low and it would run rough until the idle was brought back to normal. Any attempt to add throttle after letting off the throttle while the rpms were falling would cause it to stumble and break up and if you were too heavy on the gas when doing so it would backfire through the intake. I pulled apart my backup TPS, checked the insides (looked clean) and put it back on the car and honestly could not tell any difference between it and the one that had been running the car without issue. It's weird as I have tried to start the car after testing the various components so I would have some kind of idea as to what the issue originally was but I don't really know what I could have done to make it work (somewhat poorly) now. I tried all three computers today before taking anything apart (back to the original computer) and the car would just start/die instantly. The only thing I have not really messed with is the idle valve (early car) and am not sure it would cause the issues I am experiencing.

The videos I think are in chronological order of how things progressed

Gasngo

A long shot but how about a new or known good Ing coil. They do break down. I have had no starts and poor performance issues during the Mech. years especially in high humidity. I know this started before we went from Sahara to Nimbus 3 but give it a try.

papasmurf

I did check the coil saturday as far as voltage from the battery to the coil and an ohms test on the primary/secondary. I am not saying that could not be the problem but it did pass the tests I could find for it online.