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Chevrolet Astro 4.3 1997 - Non start - Fixed #

Posted by Pete Mutlow on September 18, 2013, 5:05 pm

Year of Manufacture *: 1997
Engine Size and Code *: 4.3 ltr
( Optional ) ECU Type: n/k
( Optional ) Scanner Used: Autocom
( Optional) Fault Codes: None

Greetings,

I would value opinions on this little problem.

The Vehicle. This is an American import for those who don't know and is a V6 (Auto). Fuel injected and looks similar to the Ford V6 engine as seen in the old Granadas etc. Also runs on LPG.

Background. Owner was driving at approx. 50mph over bumpy ground and cut out. Driver switched over to petrol and still non-start.

My Checks. No fault codes and little useful live data shown. HT present using special Crypton gizmo and fuel present as shown as 5000+ ppm HC. No response from a "sniff". Vehicle cranks well but not firing. Compressions on all cylinders show on average 150 PSI. Timing checked and OK. Now heres the thing. I wanted to find out what the vacuum was on cranking which was 15" hg on WOT with throttle intake covered. This test resulted in the vehicle firing for a few seconds and will do so now when trying to start it normally with everything intact. So this vacuum test has now prompted the engine to fire and run for a few seconds but will not rev.

My Thoughts. I think the cat may be blocked but want to elicit opinions before going down this road. The vehicle was driving down a bumpy road and when it cut out it prompted the owners wife to think something has "dropped off".

Many thanks in advance for your collective wisdom.

Regards

Pete M

Re: Chevrolet Astro = Non-start

Posted by Alan Lange <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=ukat3293' width='330' height='300' border=0 style='border:none;'> on September 18, 2013, 8:14 pm, in reply to "Chevrolet Astro = Non-start"

A little info here Pete, I think it covers your year. Looks like there is no fuel cut-off switch(uses the oil pressure switch to know if the engine is turning). http://www.astrosafari.com/download/file.php?id=1063&mode=view

Re: Chevrolet Astro = Non-start

Posted by Pete Mutlow <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1569' width='330' height='300' border=0 style='border:none;'> on September 18, 2013, 10:22 pm, in reply to "Re: Chevrolet Astro = Non-start"
Peter Mutlow

Hi Alan,

Thanks for that. Sounds like the same system as used on the old big Rover SD1's. But....if all the ingredients are there to start the vehicle which they are, then the vehicle should start and run?

Regards

Pete M

Re: Chevrolet Astro = Non-start

Probably way off the mark but could the sump have been hit breaking the oil pick-up pipe? Fuel pump will run on cranking for a few seconds then oil pressure should take over. Not sure if the gas would use the same system but it's possible. Wouldn't explain why it wouldn't start on a sniff though.

Update

Posted by Pete Mutlow <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1569' width='330' height='300' border=0 style='border:none;'> on September 21, 2013, 12:08 pm, in reply to "Re: Chevrolet Astro = Non-start"
Peter Mutlow

Greetings,

Part of the exhaust on one side of the V engine was loosened off and still no start which rules out a blocked cat/exhaust. Will have to go back for another look and would appreciate any further thoughts prior to this.

Regards

Pete M

Re: Update

Posted by Mark Carter <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on September 22, 2013, 9:36 am, in reply to "Update"
Mark Carter

What's the fuel pressure actually reading?

What are the burn time and KV readings?

What injector duration is the ECU commanding ?

Mark

Modern cars, Its all wizardry and witchcraft

Re: Update

Posted by Pete Mutlow <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1569' width='330' height='300' border=0 style='border:none;'> on September 22, 2013, 4:10 pm, in reply to "Re: Update"
Peter Mutlow

Hi Mark,

Thanks for your input. However, this thing stopped when it was on LPG and refused to re-start on petrol so I am thinking it is something common to both types of fuel system rather than petrol which your tests are suggesting. I am going to look at the ignition side again as you have suggested although I am seeing a nice HT spark both physically and through the Crypton HT Tester, Also, in my experience I have found that if a vehicle fails to fire on a "sniff", then the fault is usually either ignition or mechanically related. I just find it odd that it now fires with the throttle body blocked off which would perhaps indicate a very lean mixture but no obvious air leaks are present. Also, because the spark plugs are very inaccessible it was difficult to see if there was a serious over-fuelling issue going on. This will be checked on my next visit.

Regards

Pete M

Fixed #

Posted by Pete Mutlow on September 24, 2013, 7:27 pm, in reply to "Re: Update"
Edited by board administrator October 2, 2013, 4:13 pm

Greetings,

I am embarrassed to say I am wearing sack cloth and ashes on this one by failing to spot a very basic diagnostic error.

I went back to the vehicle yesterday morning with an open mind and re-conducted the usual basic checks. Not firing on a "sniff" and plenty of HC's at the tail pipe. I then checked for HT the "old fashioned way" without using my 20 yr old Crypton tester and found a weak and intermittent spark at a plug lead and also at the main HT Lead.

Customer managed to get hold of another coil/amplifier pack and the vehicle fired up about an hour ago.

It just goes to show how mistakes can be made and my only consolation is that the previous mobile mechanic "tested" the HT as Ok as well and that it was me that found the problem and not someone else. Incidentally, I re-tested again with my HT tester and that still showed the HT as good. That piece of kit is now in the bin.

Thanks all for your interest, I am now going to lie down in a darkened room.

Regards

Pete M

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