michael2e

I'd appreciate any ideas to help me figure out why I'm having trouble with starting when my engine is cold. I performed a major rebuild on her last year including a new Vitesse Stage 2 MAF kit and she has run perfectly for about 10000 miles until just the past couple of weeks. The car starts and runs normally throughout the day but just first thing in the morning when cold she'll crank but no fire. After perhaps 4-6 tries I'll get a random fire and then after a few more tries it will usually start but run very rough and kill as soon as I open the throttle. Another attempt or two and she'll gradually begin acting normally if I feather in some throttle. Once I can get her reving over 1500-2000 then she'll run great the rest of the day. Here's what I do know:

1. Fuel rail pressure gauge reads 50 PSI immediately
2. Fuel injectors were new (Bosch 55#) with rebuild last year
3. I smell fuel after trying to crank
4. When I pull plugs I smell fuel on them
5. Cap, plugs and Magnecor 8.5 wires are all new. Coil is original. Rotor is old
6. Compression is normal and equal in all 4 cylinders
7. No coolant in cylinders and normal pressure in the cooling system
8. HG (MLS) replaced last year with rebuild. Only sees max15-16 PSI boost
9. No unusual smoke out tailpipe
10. Metering system is Vitesse MAF that has temp analysis
11. Replaced SMT6 tuning module with test circuit to no benefit
12. Swapped out 2 different DME relays without change
13. Visual inspection of coil and each plug wire shows spark while cranking
14. Timing check -spot on
15. Tach bounces while cranking however flywheel sensors are aged
16. Vacuum reads 12-14 once idling
17 Oxygen sensor (Bosch) about 3 years old
18 TPS is original
19 Wiring harness is original

Very sporadically over the past couple months I was having an issue with no crank and dead instruments when the key was turned to the start position. After cleaning and tightening all battery cable connections, and cleaning the DME relay connections in the relay board this problem has appeared to resolve. I also had to replace the brushes on my alternator which was rebuilt only 2 years ago. Since the battery and P/N cables are relatively new, I gathered that the alternator cable which was the original was probably the culprit causing excessive load and wearing down the brushes. So this was replaced recently as well.

What else should I check? I havent had to take my car to a mechanic for over 5 years, sure'd hate to do it for this seemingly simple problem but I cant think of anything else. Your help is very much appreciated Rennlist.

fast951

Check the followings:

- Fuel Pressure at fuel rail before & during starting procedure.
- How old/condition of: the coil? The plugs? The O2 sensor?
- Check TPS

If the car was running fine, then started acting up after some electrical work, go back and double check the work you have done..

michael2e

thanks John, I know I can always count on your assistance.

1. With key on - no fuel pressure. Builds rapidly to 45-50 PSI while cranking and then stays there.

2. Plugs are Bosch Platinums about 3 days old
3. Dont know how old the coil is - at least 8 years. I was under the impression that these last for quite awhile. If this is inaccurate is there a way to test it?

4 TPS is also old. How to test?
5 Bosch sensor new 3 years ago

Thanks for your help

fast951

The No-Fuel-Pressure at startup is something I would like to investigate further... Build fuel pressure, let the car sit (not running & ign off). How long does the pressure stays high or when does it start to bleed.. How long does it take to go to zero pressure?? A leaky injector will drain the fuel pressure and will cause starting problems.

- Once the car starts and warm, does it start quickly? If yes, then TPS more than likely fine.
- Before starting the car and when zero fuel pressure. Pull the plugs out and notice any fuel or fuel smell.

quinnfiske

Since your problem only happens when the engine is dead cold, perhaps the DME water temp sensor is the culprit. I tested mine with help from Clark's website. I removed it from the car and heated it in a pan of water. The resistance should be 3.3k ohms at 59F and 280-360 ohms at 176F.

http://www.clarks-garage.com/ Look under Sensors and guages in the Garage Shop Manual.

michael2e

Thanks again for the input guys. Well after messing with the relay board she's started up normally the last 2 mornings while cold. Since I was having trouble with the DME relay connections in the board and also an ongoing struggle getting the indicator/flasher relay to work consistently (despite a new one of those ) I started thinking about other relays that may play a role in the starting process. All of these relays sit next to each other on one side of the board.

I'll defer to the experts on the circuitry but as a test when my engine was warm and running/starting normally I tried pulling the Ignition X relay to see what would happen. I was surprised to find that the car would start without this relay but interestingly it would run very poorly and then kill within a few seconds in a very similar fashion to the problem I've been having. I cleaned up the terminals on the relay and the female ends in the board and so far she's been working fine. Makes sense that poor connections on the relay board can mimic a bad relay when actually the relay itself isn't the problem. Not sure why it would manifest only when cold if this turns out to be the culprit but I'll keep ya'all posted.

Just curious if there's a product around that one can use on electrical connections like this to dissolve corrosion/grime in areas like this that are difficult to get at?

quinnfiske

I got a can of contact cleaner at Radio Shack. It is a spray can that sprays through a plastic tube with a brush on the end. Works well in hard to reach areas.

michael2e

Quinnfiske you nailed it. Since the DME temp sensor was the original I went ahead and ordered the $25 replacement while working up the problem. When I went to put it in I took a closer look at the wiring harness and there was a short from worn/melted insulation at the connector for the sensor. All patched up and running normally again. A free day of skiing for you if you ever make it out to Aspen. Thanks again to all

quinnfiske

I glad you fixed it. Its great to be able to pay back a Rennlister for all the help I have gotten here. These forums are the best thing that has ever happened to gearheads. There are a lot of people who complain on these boards, but the reality is that it they have made ownership of exotic but ageing machinery a possibibility for a wider group of people.

michael2e

I agree - it's a shame all the bickering has cost us a lot of knowledgable people who dont peruse the list anymore. Anyway, I hope there's a good support group like this when I funally get a Ferarri. Cheers!

Dilberto

The speed sensor, RPM sender, and magnetic Hall sensor, can all evoke a no-start situation. Make sure they clear the spinning flywheel by at least .28mm> Also, the sensor wires go bad, and may be the problem, especially if no spark exists.