Breakdown today - fuelling?? - any thoughts?
Discussion
An interesting thing happened to me today.... the Ultima broke down! - well for 20 mins!
Had been out for a long drive - about 140 miles in I exited a roundabout leading to empty long uphill straight - opened her up in 2nd, 3rd, then 4th and felt a drop in power... quickly realised fuel pressure falling - eventually coasted to a stop at the crest of the ill on the flat!
My set up is LS7, ultima factory fuel system set up, with anti surge pot fed by LP pump, and HP (aeromotive) pump delivering to aeromotive regulator - standard stuff. Sucking from left tank which was about 1/2 full (right tank empty)
Normal checks - check for leaks, obvious stuff, ignition off and on, immobiliser check etc - fuel pumps appeared to prime, although HP pump sounded a bit rough. Checked pump relays, fuses etc, all ok. Phoned recovery folks, then after about 15 mins thought I'd try again - and she sprang into life, full fuel pressure all was normal.
So cancelled recovery, let her idle for a few mins then chanced my arm at the last 50 miles back home, Stopped a few miles later - brimmed both tanks - all was perfect all of the way home. Had a quick check over at home and nothing obvious at all.
First thought is maybe a slug of air in the system due to lowish fuel level in left tank combined with opening her up on a fairly steep long hill - lost prime and hence pressure.
Any other ideas?
Paul
Had been out for a long drive - about 140 miles in I exited a roundabout leading to empty long uphill straight - opened her up in 2nd, 3rd, then 4th and felt a drop in power... quickly realised fuel pressure falling - eventually coasted to a stop at the crest of the ill on the flat!
My set up is LS7, ultima factory fuel system set up, with anti surge pot fed by LP pump, and HP (aeromotive) pump delivering to aeromotive regulator - standard stuff. Sucking from left tank which was about 1/2 full (right tank empty)
Normal checks - check for leaks, obvious stuff, ignition off and on, immobiliser check etc - fuel pumps appeared to prime, although HP pump sounded a bit rough. Checked pump relays, fuses etc, all ok. Phoned recovery folks, then after about 15 mins thought I'd try again - and she sprang into life, full fuel pressure all was normal.
So cancelled recovery, let her idle for a few mins then chanced my arm at the last 50 miles back home, Stopped a few miles later - brimmed both tanks - all was perfect all of the way home. Had a quick check over at home and nothing obvious at all.
First thought is maybe a slug of air in the system due to lowish fuel level in left tank combined with opening her up on a fairly steep long hill - lost prime and hence pressure.
Any other ideas?
Paul
Ultima factory said:
This is incorrect.
Ultima fuel tanks for the last several years have the actual fuel pickups at the rear of the tanks via an internal tube even though the outlet is welded in the side. This means that the flat base design of the tanks works well as the fuel on acceleration is forced to the rear of the tank where the pickups are located so running low is not a problem.
What year was this changed, can you tell us?Ultima fuel tanks for the last several years have the actual fuel pickups at the rear of the tanks via an internal tube even though the outlet is welded in the side. This means that the flat base design of the tanks works well as the fuel on acceleration is forced to the rear of the tank where the pickups are located so running low is not a problem.
cheers
K
Ultima factory said:
This is incorrect.
Ultima fuel tanks for the last several years have the actual fuel pickups at the rear of the tanks via an internal tube even though the outlet is welded in the side. This means that the flat base design of the tanks works well as the fuel on acceleration is forced to the rear of the tank where the pickups are located so running low is not a problem.
Good idea, much better place to have it..Ultima fuel tanks for the last several years have the actual fuel pickups at the rear of the tanks via an internal tube even though the outlet is welded in the side. This means that the flat base design of the tanks works well as the fuel on acceleration is forced to the rear of the tank where the pickups are located so running low is not a problem.
Ultima factory said:
7litrebig,
Our theory in this particular case is that when the engine was used on full power up to fourth gear the surge tank ran dry introducing air into the system. The likely reason that this tank ran dry is the gauze filter in the base of the low pressure lift pump became blocked with debris. This filter is accessed by removing the pump base plate held on by four screws.
The reason that the car runs ok at present is that the extra head of fuel introduced by filling the tanks as well as not using full power for a period of time means that the low pressure pump can just cope with that situation.
Worth checking out.
Many thanks for the advice Factory - I'll check it out - I have run the tanks pretty low on occasion during long runs, and have 7k on her now, so although in this instance the left tank was 1/2 full I wouldn't be surprised if the filter needed checking.Our theory in this particular case is that when the engine was used on full power up to fourth gear the surge tank ran dry introducing air into the system. The likely reason that this tank ran dry is the gauze filter in the base of the low pressure lift pump became blocked with debris. This filter is accessed by removing the pump base plate held on by four screws.
The reason that the car runs ok at present is that the extra head of fuel introduced by filling the tanks as well as not using full power for a period of time means that the low pressure pump can just cope with that situation.
Worth checking out.
Thanks again to all for your responses - most helpful
Paul
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