dfroelicher

I purchased an 83 us 928S in june of last year (05) and had no problems...until now!!

about 4 months after i bought it it started to take longer to catch, would still turn over just fine and at the same speed, just more cranks before catching and starting up. then about a couple of months ago it started not starting in the morning.

Come out in the morning and cranks just fine, no start. If you came back in the afternoon, say noon or 1 oclock, it would fire up just fine. Also if you used a jumper pack it would start right up regardless of outside temp.

About a month ago mid to early Jan. of 06, it just stopped. End of story. cranks fine, radio works, clock works, no other apparent problems.

Last night replaced the fuel pump (whoops forgot to drain tank, that was fun) and found that power may or maynot be getting back to the pump.

So, after all that my question is, WTF , am I looking in the wrong place, does anyone have any similar experiences with the fuel system and or vehicle. Would really like to stay away from computer stuff and major cost type repairs, unless that is the only way to fix it.

Thanks for any help and feel free to private message or e-mail.

khalloudy

temp ii sensor. had the same problem on my 87 s4, a $40 solution... drove me crazy till i diagnosed it. PM me if you want the details.

Rich9928p

The L-Jet injection system in the '83 is different from the LH in the S4s. The L-Jet has an "external" cold start system, where the LH uses 2x the injection pulses for cold start enrichment.

Jim Morehouse's CD-ROM tech docs provide all the detail needed to check out L-Jet fuel injection systems. Don't overlook vacuum leaks. There are a lot of hoses that get old and crack. Cold temps can make things worse.

SharkSkin

Try jumpering the fuel pump relay. Check all fuses. Double-check that you have the polarity right on the fuel pump terminals. Take two aspirin & call me in the morning.

justin

On MY 1980, it was problem for years, then I changed the temp sensor, and volla, it quit.

dfroelicher

Jumpered the pump and pump runs fine, have not heard the pump running with the relay in circuit, but pump runs and engine wont start, any info on the relays testing prodcedures and specs would be helpfull.

vehicle still wont start

also any help with what the temp sensor should be running at would help.

thanks for all your help guys


Long live the 928 (just not mine )

justin

Front of the engine.

justin

Wow thats big, sorry guys, and my engine is diiirty!

khalloudy

I suggest you replaced the temp sensor that Justin indicated in the picture, from the symptoms, i would bet money it is the culprit. Diagnosing is is sometimes easy sometimes not. Mine worked fine excpet in very low temperatures where is went into open loop (infinity resistance) and hence we could never diagnose it correctly until i asked my mechanic to take the car home with him and heep it out overnight... then voila, it was the temp sensor.

Rich9928p

The fuel pump doesn't run until the engine speed reaches 50 RPM. This is a safety feature. If a fuel line is cut and the engine stops running, the pump shuts off - so fuel is not sparyed all over!! So, you will not hear the fuel pump running when the ignition switch is on, but the engine is not turning.

The temp I and II sensors signal tells the L-Jet how much fuel enrichment is needed. As I previously mentioned, the L-Jet system has a separate cold start system that includes a cold start valve (add'l fuel sqirt) and an auxiliary air regulator (faster idle speed).

The Temp II sensor has two wires, for two sensors included into one plug.
To test the sensors, you measure the resistance from the pin and an engine ground point (not between the two pins!).

Temp II sensor:
10 C / 14 F 7 to 12 k-ohm
20 C / 68 F 2 to 3 k-ohm
80 C / 176 F 250 to 400 ohm

Cold start valve Temp I (brown plug):

Note: when the “connector locator notch protrudes inward to the pins from the top, the left pin is Terminal W and the right one is Terminal G.

Terminal “G” and “ground”
below 30 C / 86 F: 0 ohms
above 40 C / 104 F: 100 – 160 ohm

Terminal “W” and “ground”
below 30 C / 86 F: 0 ohms
above 40 C / 104 F: 100 – 160 ohm

Terminal “G” and terminal “W”
below 30 C / 86 F: 25 – 40 ohms
above 40 C / 104 F: 50 – 80 ohm

If the temperature sensors test out within spec, I suggest checking out the full system. This is how the system works. AFC [Air Fuel Control] relay XVI pin 30 always has 12 Volts regardless of ignition switch position. The AFC relay switches between relay socket pins 30 and 87, and the 12V at pin 87 then goes to the fuel injectors. [Note, even though it is not shown on the schematic, I've been informed that there are two AFC relay socket position 87s, so a jumper needs to have two leads out from the 30 position to connect to the two 87 positions]

a. Measure voltage at pin 30

-- If 12V present, next (with ignition turned on) is there 12V at pin 87?

If yes go to (b)

-- If no, check the connection at the battery. A direct cable connects the battery to the AFC relay pin 30. Is there 12V at pin 15? If there is no voltage, the ignition switch could be bad or the path between the ignition switch and AFC relay has an open or short circuit.

b) is there 12V at the fuel injectors (pick any one to check)?

-- If yes, this says that your problem is with the fuel injection "ground" path. Go to (c)

-- if no, there is a wiring problem between the AFC relay and fuel injectors.

c) is there 12V at L-Jet connector pin 10 and 29?

-- if no, there is a wiring problem between AFC relay pin 87 and L-Jet connector pin 10 and 29.

-- If yes, check grounds for the L-jet controller. L-Jet connector pins 5, 16, 17 and 35 should have a very low resistance (via ohm check) to ground. For this check, set your VOM to Ohm mode and measure the resistance between the L-Jet connectors and a ground point on the car. If the Ohm reading is high to infinite, there is a wiring or connector problem with the ground points. If the Ohm reading is low, I'd say the L-Jet is bad.

Hope this helps.

dfroelicher

thanks alot for all your help guys.

Rich, that is a lot of really good info can't wait to try it out.

anybody have any info on how to test the fuel pump relay? hate to sh*t can it if I dont have to.

also if you could include some info on volt meters, I'm having a tuff time translating the digital ohmage read out (dial set to 2k open circuit reads 0.00, does that mean percentage of 2k or if read out says -3.05 does that mean more?)

anyway you guys have been invaluable to the community, thanks alot

Bill Ball

You jumpered ther FP relay, so no need to test it, Since jumpering it didn't fix your problem, move on to the other tests. Temp sensor 2 sounds like good candidate. Get a cheap meter that has an AUTO setting so you don't have to worry about ohm settings.

dfroelicher

I have an expensive equus tester and should have bought a book to go with it.

My question is that I think I have two problems and would like to not have to pay twice for shipping and handling. The jumpering test only tells me that the puimp and wiring back to it are good, not the relay itself.

dfroelicher

Tested the temp sensors today and came out with some interesting results.

On the Temp II sensor between either plug and ground is infinite ohmage (open circuit) currently a balmy 50 degrees in the phoenix area.

The temp I sensor showed from what I can tell, to be ok.

Still have not found any info on the relay test procedures, dont know if that is faulty or not

Well, looks like I'll be giving Mark a call here soon (go Big 3).

Once again thanks for all your help guys and especialy to Rich, thanks alot for all that info .

khalloudy

As i said in my previous post.... i had the EXACT same problem... infinite resitance at low temperature is what i saw in my S4 and was causing the same cold start problem and symptoms.... it should be in 5k Ohm range instead of infinity in cold weather... so i think there is you problem.