M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: KidneyBoy on January 10, 2010, 11:13:54 AM
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Im working on a car i sold to a friend about a year ago. I rebuilt the head and gave him the car in good working order.
Since then, it has had an issue where it will not start after running a short distance. I had thought it was a charge/draw issue and worked to solve this. It now holds a charge [which it did not before] but if the car is started and ran around the block [1-2min of run time] then stopped it will not start.
Cranks and tries to fire. Sputters while cranking, once cranking is stopped it continues to chug for a second or two then dies. Has fuel, has spark.
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I know it gets fuel, but double-check to see if the fuel pressure is good.
I've heard of a BMW fix that puts a valve in the output line off the tank pump. Here's a write-up. (http://www.m42club.com/forums/showthread.php?t=4688) The pump bleeds off pressure after a warm start & the car takes forever to start.
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Well, the fuel pressure should not cause it to act that way [going to check pressure anyway]
It literally will run like a champ [perfect idle, good power, smooth, quiet, etc.] but if you turn it off then immediately try to start it again it will not start. it cranks and cranks, tries to fire and sputters out.
Wait an hour or so and starts on the first try and runs great.
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Well, let me know what you find. Post stomp test results too...could be a flaky coolant temp sensor, FPR or leaky injectors too.
I suspect that the pump is a little slow to pressurize the system on warm starts but it's just a hunch.
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the PO removed the wiring for the check engine, i cannot find it anywhere behind the cluster. i was thinking the temp sensor or coils.
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Fuel pressure figures...
50lbs when cranking
40lbs @ idle
35-45lbs while running
36lbs when turned off
Then when it wont start
50lbs cranking
46lbs after cranking
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Those pressures sound great. FPR & fuel system check out.
Temp sensor on head or O2? Maybe the temp sensor is reading too warm (or O2 too low) & the DME isn't injecting enough fuel? Odd that the pressure remains high on the warm start.
Maybe the O2 heater or relay is dead & not warming up fast enough? If the car is hot the O2 will be in normal closed-loop mode. If it's warm the reading might be off, leaning out the mixture & keeping the car from starting? Just a guess...
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can you give me some figures to check?
crank/cam sensor ~600ohm
afm 4k-8k between pins 1 & 2
TPS 1.9-5v
Whats the range for the temp sensor?
02?
Ive got a spare ECU/DME that my friend is going to let me try.
Some more info.... I can start the car, let it run for 30 seconds then restart it all day long. It has to run for about 2 minutes before it wont start. After about 20-30 minutes it will start fine.
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where are the ground for the engine harness?
i know of the one near the pass tower [where the battery used to go] and another off the pass motor mount. are there any others?
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I may have the crank and cam backward
Crank Sensor - 1257 ohm
Cam Sensor - 508 ohm
AFM checks out, in range from 4k to 8k then back down to 4k
TPS 4.72v to 1.17v
ECU temp sensor - 620 ohm cold
How do i check the coil packs?
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I've never tested the packs. I'd pull the plugs out, reconnect them & ground them to the engine to see if they spark. I'm sure there's a better test, but I haven't ever done it any differently.
The sensors you tested seem OK, readings all are pretty normal. Crank & Cam values are reversed. Did you test the O2 heater relay?
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How is the o2 heater relay checked?
sorry for coming off as 'needy' but im quite tired of this car
:(
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Okay, I've done a bit of work on the car since the last post.
Heres what I've found...
Car runs fine after sitting for a while but will NOT restart after being turned off.
CPS, CMS, ECU temp switch, AFM are all in good working order.
What Ive found in playing around, is that the engine floods when turned off. I have swapped FPR's with no luck. The fuel pressure is good [40lbs] and will hold 40lbs after the car is shut off.
However, if you pull the fuel pump fuse [#11] and crank the car after it has been turned off, it will start and run until the injectors use the fuel in the rail.
So Ive concluded that the engine could be doing one of two things. It is either dumping fuel on start up, but only after it has been turned off within about 5 minutes. Or when the car is shutting down, i.e. ignition cut = no spark, the injectors are still firing.
This has me very confused... I'm sure someone out there in internets land has an answer.
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Wait, let's think this through. What should the system be doing on warm starts? Hopefully it's not doing the whole cold-start routine, choking the engine. That'd flood it and stop it from starting. The DME should interpret from the coolant & IAT sensors what to do, how far to richen up the mix. Coolant sensor checks out at all temps, right? I found these figures at bimmerforums (http://forums.bimmerforums.com/forum/showthread.php?t=904942), not sure if they're right:
-10 +- 1C.....7-11.6k
20 +- 1C.......2.1-2.9k
80 +- 1C.......0.27-.40k
They're for an e36, but it's likely the same sensor. I'm assuming ohms resistance.
Can you get a spare AFM?
Here's some info (http://forums.bimmerforums.com/forum/showthread.php?t=1293914) about the IAC sensor:
It is nothing more than a NTC thermistor, connected in series with a 1kohm resistor in the ECU...you can just use this one:
http://search.digikey.com/scripts/Dk...me=490-4665-ND
Isn't that from a member of this board? Stand up & be recognized if so...excellent bit of reverse engineering there!
The injectors should continue to fire even if the pump isn't on. They're fired from the DME & only pressurized by the pump. The FPR is mechanical, so the DME really has no idea about the precise fuel pressure/temperature or vacuum enrichment. Bosch & BMW do a lot of things like that...for instance the little MPG gauge is just a calculator figuring injector duty cycle against the speedo reading, corrected by the settings on the EEPROMs in the cluster & trip computer.
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Well, it all seems to check out, do you know what pins i can back check on the AFM to make sure the internal temp is reading okay? Or even a reading, cause i can see the thermocoupler with the air box off.
I did fixed the wiring from the check engine light. The battery had been disconnected for some time and the car has only been started a handful of times since then.
Only code 1216 which is the TPS but could be the connector.
I may have to give the car back to my friend and have him drive it around occasionally doing a stomp test.
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Sounds like you're making progress... You're right about that 1216 code...might be the harness. That shouldn't have anything to do with the warm start issue. I'm not sure what pins the AFM thermo is on...I have to dig out the old Bentley.
I hate chasing wiring problems, but that's what I have to live with to drive an e30. Just had her out today...sun broke through after nearly two weeks overcast. Sweet.
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Well, heres a little more insight..
I talked to my friend, he says if you drive the car for a while [30 minutes] it will start up fine after being turned off. The issue is when the car has been running for only a few minutes and is then turned off [before coming up to op temp] then it will not start.
I noticed a lot of water coming out of the tail pipe, and some in the intake boot. Has no smell, looks brownish. No major vacuum leaks and i had the head pressure check when it was rebuilt.
The plugs are dirty, so the car is running rich even when it running fine.
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Yeah...something isn't cutting off the cold start enrichment. It's likely running something like 5 to 1 ratio; there's no way a warm engine will start like that. Getting another AFM to test might not do it either...they're all so old now, who knows what those sensors will do?
I get a bit of water out of the pipe too, how much is a lot? Water condensing in the intake can be normal too in cold weather, but I would worry if it's enough to be sloshing around. Happily mine has enough oil to drive off the water!
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Ive got a 318is myself that has run like a champ for 6 years now, never once let me down **knock on wood**
i can try my AFM on it but i hate throwing things at it without knowing exactly why is not working right.
Is the O2 sensor cut out on a cold start up? im pretty sure thats how it works. The only major peice of sensor i have not checked at all is the O2 sensor.
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No, the O2 sensor will take a while to heat itself up, then signal the DME that it's up to temperature. That (and coolant temp) will switch the DME into the more economical 'closed loop' (except at wide-open throttle).
I think the O2 heater relay is closest to the driver's fender of the three firewall relays.
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Well today i told my friend that the car was ready for him. Before i was to drop it off, i decided to do the stomp test and see if it threw a code. And what do you know, the CEL didnt do anything.
So i thought i found it. Check the connection to the TPS and it was fine, checked it all the way back to the ECU and it was fine. Threw the car back together and the damn thing started idling at 4200rpm. Check the temp sensor, checked the temp wires to the ECU. All was fine, just like before.
My friend lent me a spare ECU if it came down to it. So i tossed it in and guess what....
Heres the old one after i opened it up:
(http://www.r3vlimited.com/gallery/files/1/1/0/4/7/dscn5281.jpg)
FleaBay chip FTL
(http://www.r3vlimited.com/gallery/files/1/1/0/4/7/dscn5283.jpg)
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Pin 43 Common 5v Coolant and TPS BR/BK
Coolant?
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Damn...that DME trace is cooked! To be totally fair, the chip might not be the culprit. Might just be a short in the harness...those traces can't tolerate 12v for long.
Swapping parts FTW.
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yeah, i know the chip was not at fault, wish it was that easy.
I hooked up the battery without the ECU and plugged into pin 43 and a ground... only .4v going through it. Wiggled some stuff around and it did not jump.
This car has had a hard life, i bought it from a friend with a bad head. It was a 318is, then got an M20 swap, then back to the M42. Im banking on some error when the PO put one of the few engines that have been in this car.
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I don't know what that pin 43 is for. I found a reference to "CO Pot." It's for non-cat models, perhaps it's the infamous wire on the firewall? On non-cat models it senses the CO screw on the throttle body & adjusts CO electronically somehow.
I love e30s...they all seem to have a story. BMWs are a bit like legos too; mostly all the parts fit.
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Pin 43 is the common ground for the TPS and Coolant sensor
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Hmmm. I'll add that to my documentation. Do you have a complete pinout of the Motronic?
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From another source...
Motronic Control unit
Function Color
1 Fuel Pump Relay BR/GN
2
3 Injectors 1-3 BR/WT
4
5
6 Ground BR/OR
7
8 Check Engine light BR
9
10
11
12 TPS Signal 5v BR
13
14 Common 5v GY/BU
15
16 Camshaft sensor input YL
17 Fuel rate output WT
18
19
20
21
22
23
24 Ignition cyl 3 BK
25 Ignition cyl 1 BK
26 Power Input RD/WT
27 Main Relay control BR
28 Ground BR/OR
29 Idle Speed Control WT/YL
30
31
32 Injectors 2-4 BR/WT
33
34 Ground
35
36 Charcoal Canister control BR
37 O2 relay control BR/GN
38
39
40
41 AFM Input (5v) GY/YL
42
43 Common 5v Coolant and TPS BR/BK
44 Camshaft sensor input BK
45
46
47
48
49
50
51 Ignition cyl 4 BK
52 Ignition cyl 2 BK
53
54 Power Input RD/WT
55 Ground
56 Start Input GN/YL
57
58
59 Refrence output (Ground??) GY/WT
60
61
62
63
64
65
66
67 Crankshaft input sensor BK
68 Crankshaft input sensor YL
69
70 O2 Input BK
71 O2 Ground YL
72
73 Speed Signal input BK/WT
74 Engine Speed Output
75
76
77 Air temp input GY/VI
78 Coolant temp input BR/RD
79
80 Diagnostic voltage GN/BU
81
82
83
84
85 A/C Input BK/GY
86 A/C Input BK/VI
87 RXD Diagnostic WT/YL
88 TXD Diagnistic WT/VI