Aston Martin DB7 won't start

rugbyman · 03-01-2019 11:07pm #1

Hello All, I have had a 2001 DB7 for five years. it lives outside and has not yet done 1000 miles in my ownership. it has killed four new batteries. This is not unknown for that year and i can only blame myself for continuing this waste. So i have good experience of battery problems
The car was left unused, recently, for a while.then turned over quickly but would not start.

I should have mentioned that on four of five occasions over the years the car could cut out and stop while driving. A moment later I could restart it,instantly.

I replaced a Lambda sensor recently ,

Unsure of the petrol level we put two gallons in, the guage reads 1/4 full. The engine spins merrily, the fuel pump relays seem ok,i do not have a chart showing which fuses are relevant,and have not checked any of them yet.

Having read of the fuel valves at the ends of each fuel rail on top of the engine, i checked them today
The one on the N/S rail showed no fuel. The one on the O/S did spurt, and on several swithing on of the ignition key ,spurted(on pushing a match in) each time.

This suggests to me that one of my two fuel pumps works. Still the engine does not fire.
I propose to try some easy start to ascertain if the problem is ignition related.

I have a good mechanic ,who has a computer,compatable with the DB7, but he is unavailable

I am trying to educate myself in the meantime

Any suggestions, thanks in advance

Rugbyman

scannerd · 03-01-2019 11:51pm

The long term lack of use would make me worry about the fuel system, petrol goes off after a few months and it can then clog up the system, plus it will not burn. You have added new petrol but if the old as bad that could still effect starting. Pressure is also a good test, which you seem to have checked

After that you need spark, compression, then timing.

to test spark pull 1 plug, hold against the block and get someone to crank, and look for spark on that plug

turning over faster than normal, might just be from sitting, ie the oil needed for cylinders to make good compression has all dripped back to the pan, but that should resolve after a few times turning over, if not the could also be related to the fuel issue - washing the cylinders dry

classics need using regularly, even if just running parked for 30 min once a month

Bigus · 04-01-2019 12:50am

Just to add to above , jaguars of this era and similar engine used to suffer terribly from non starting issues , particularly if they were moved a few feet when cold and shut down before they reached operating temperature.
Compression was lost across all cylinders from raw cold start enriched fuel washing the rings free of oil.
The official jaguar cure was to remove the plugs and squirt in a drop of engine oil to all cylinders, clean and heat plugs and refit and start on a newly charged battery at full throttle opening , and repeat if necessary, and if they did start, it was with clouds of smoke.
Once I got one to start that was parked in an awkward position by running two hairdryers in the engine bay for 40 mins and then one up the air intake (instead of changing plugs)along with a fullycharged battery and lots of turning over before it spluttered into life .

rugbyman · 04-01-2019 12:56am

That's some story Bigus,strange thing is the engine whirrs fast when turning over,almost as if plugs were out. Hopefully my solution, when found, Will be simplr

tabby aspreme · 04-01-2019 1:24am

rugbyman wrote: »

That's some story Bigus,strange thing is the engine whirrs fast when turning over,almost as if plugs were out. Hopefully my solution, when found, Will be simplr

If it's turning over that fast, it sounds like a lack of compression

johnayo · 04-01-2019 1:38am

As Bigus has said.......

If started and stopped without running for a few minutes to warm up, the next time you try the engine may flood. You will then get petrol wash in the cylinders where the petrol washes the oil from the cylinder walls. With the oil washed away, you will lose compression hence the engine turning over quickly.
This can happen in any petrol engined vehicle.

Isambard · 04-01-2019 4:47am

as for batteries, I have a solar trickle charger on my not in use vehicles which works very well (even under my carport and on the garage window respectively) and cost much less than a battery.

Bigus · 04-01-2019 9:49am

rugbyman wrote: »

That's some story Bigus,strange thing is the engine whirrs fast when turning over,almost as if plugs were out. Hopefully my solution, when found, Will be simplr

It's a lot simpler then a holed piston/broken ring or bent valves.

That turning over fast is exactly the symptom , you'd swear all the valves were bent from a slipped timing chain, funnily enough I had a neighbour's 152 sport cross petrol Polo with the exact same issue( moved a few feet at Christmas and left for 10 days ) , except vigorous turning over eventually started it .

So in your case , plugs out , drop of oil ( not too much to cause hydraulic lock) , turn over with plugs out , plugs in and start. Repeat if necessary til you get compression, or starts.

rugbyman · 04-01-2019 10:05am

Thanks all.... Bigus ,if thats the route to take, then even that will be some work, the plugs are not visible to me.!!!!. thanks again

Dades · 04-01-2019 1:11pm

Consider buying a lithium jump starter if you're doing a lot of cranking.

Will charge quicker and offer a lot of crank power. Might save you waiting a day a time to charge your battery every time you deplete it.

fancy pigeon · 04-01-2019 1:28pm

Does the DB7 have Nikasil coated cylinders?

rugbyman · 04-01-2019 1:55pm

Fancy pidgeon, i dont know, i assume(often a dangerous thing to do) that you are on the same track as several other people on here have suggested . on the Aston Martin owners forum Nikasil has not been mentioned

rugbyman · 04-01-2019 1:58pm

as part of my studies on this issue, i have found out that relays clicking does not neccessarily mean they are Ok

also i found that DB7 (ford parts) have lots of glitches

MercMad · 07-01-2019 10:50am

There is some mis information here.and you haven't told us the exact engine type. The compression is.being list because the lifters have drained, squirting oil in does not help this. You have most likely flooded the engine by now. Charge the battery, remove the pump fuses or relays, and turn the engine over until it sounds normal, ie the lifters have re filled. This can only happen by turning the engine on the starter until oil is pumped back into the lifters.

Be careful not to overburden the starter, bursts of 15 seconds max and 30 seconds to cool

Now reconnect the fuel pump fuse or relays and try it. If you are lucky it will start eventually. If not you will need new plugs atbthe very least.

BTW the battery should be disconnected when not in use.

Bigus · 07-01-2019 9:48pm

MercMad wrote: »

There is some mis information here.and you haven't told us the exact engine type. The compression is.being list because the lifters have drained, squirting oil in does not help this. You have most likely flooded the engine by now. Charge the battery, remove the pump fuses or relays, and turn the engine over until it sounds normal, ie the lifters have re filled. This can only happen by turning the engine on the starter until oil is pumped back into the lifters.

Be careful not to overburden the starter, bursts of 15 seconds max and 30 seconds to cool

Now reconnect the fuel pump fuse or relays and try it. If you are lucky it will start eventually. If not you will need new plugs atbthe very least.

BTW the battery should be disconnected when not in use.

Unless it's a Virage V8 it has a Jaguar based engine as can be deduced from the op's description.
From wiki
"the car was designed by Ian Callum and Keith Helfet. The six-cylinder DB7 (based on the Jaguar non-supercharged engine AJ6"

Also the assertion that the lifters draining could cause a loss of compression is fundamentally wrong as the valves would be stuck closed in this case or at least not fully opening.

The above flooding advice is based on a Jaguar service bulletin , and it is a Jaguar based engine and fuelling system , therefore the advice holds.

Henry Ford III · 07-01-2019 11:00pm

1/. Check for spark.

2/. Check for fuel delivery.

rugbyman · 08-01-2019 12:44pm

Thank you all for suggestions
The engine is a V12. I have done some reading on the A.M club page. these cars give quite a bit of bother with relays ,wiring,and fuel pumps(ford mondeo)
replacing the fuel pumps is a 12 hour job

Apparently each bank of six cylinders are fed by a seperate pump.

I have just gotten a fuse diagram and intend to check these today, the relays seem ok(they click)

on the advice of club members i uncovered the fuel rails running the length of the engine, at the end of each is a valve(schrader?) like a bicycle valve, pushing a match gets fuel from one of these but not the other, again i am told a pressure test here is a good idea

Regarding lack of compression, i have said that the engine whirrs over quickly ,but i cannot say this is not normal,because over four years the engine always started on the first push of the button, so I would not have heard it before ,as i now hear it.

Sorry ,I should have said that on a few occasions over the years the car stopped,while driving ,as suddenly as if the engine had been switched off. It immediately started when tried. On a run ,driven by a friend a few months ago it did this four or five times, the next day ,with me ,it drove 30 miles without fault

Last question chaps,,, when the expert mechanic with a suitable computer arrives next week, will his computer simply diagnose the issue, are computers that magic?

Kenny Logins · 08-01-2019 1:11pm

Can you bypass the fuel pump relay on that side? I had a similar issue on an old BMW and pulling the relay and connecting the terminals would allow the pump to run regardless.
Tapping the relay with a screwdriver handle also got the car going on more than one occasion.

Bigus · 08-01-2019 6:45pm

In fairness V 12 's sound like no compression even when 100% healthy as they are perfectly balanced, so the starter just give a constant sound.

TeaBagMania · 08-01-2019 7:05pm

there are many reasons for an engine to stop dead in its tracks like you described, my experience it has been the crank position sensor, just food for thought.

sounds like one of the fuel pumps isn't working, could be just a bad armature on the pump motor.
try knocking on the fuel tank a few times with a rubber mallet, sometimes its just enough vibration to get the motor to move a bit and make contact with the next armature, once running it will have enough momentum to spin past the bad one.

let us know how she does, and get some miles on that girl

rugbyman · 08-01-2019 11:58pm

Thanks all.any opinions on how magic the computer diagnosis will be

galwaytt · 09-01-2019 4:19pm

rugbyman wrote: »

Thanks all.any opinions on how magic the computer diagnosis will be

Very :pac:

beertons · 09-01-2019 7:51pm

Any pics?

scannerd · 10-01-2019 7:20pm

rugbyman wrote: »

Thanks all.any opinions on how magic the computer diagnosis will be

The magic computer give you about 20% of what you need to know most of the time, i'd bet it wouldn't show any fault in this case. It gives you a direction to go but you still need to know what your looking for.

rugbyman · 12-01-2019 7:58pm

hope to have talented computer user here next wed

rugbyman · 16-01-2019 3:20pm

TeaBagMania wrote: »

there are many reasons for an engine to stop dead in its tracks like you described, my experience it has been the crank position sensor, just food for thought.

sounds like one of the fuel pumps isn't working, could be just a bad armature on the pump motor.
try knocking on the fuel tank a few times with a rubber mallet, sometimes its just enough vibration to get the motor to move a bit and make contact with the next armature, once running it will have enough momentum to spin past the bad one.

let us know how she does, and get some miles on that girl

Tea bag (ex Prison Break?right?)
The computer man arrived today,unfortunately I was not there, my competent nephew was.his computer reading was "crank shaft sensor" he went on to say it could be OK but corrosion.he is too busy to sort it for me. Could you elaborate a bit on your theory, thanks

TeaBagMania · 16-01-2019 3:39pm

When someone describes an engine shutting off strait away, no hiccups, coughs, or sputtering. its more times than not the crank position sensor.

Just remember even though the scanner reads bad CPS it could be the sensor, wiring from ECM to the sensor, or the ECM itself not interpreting the CPS signals, again, more times than not its the sensor.

I think your Aston was from the Ford era so a CPS shouldn't be too expensive, you can try cleaning the one you have but they are usually buried between the engine and transmission, so might be less expensive labor wise to just replace it unless you are performing the work yourself.

rugbyman · 16-01-2019 5:03pm

Thank you for speedy reply
few questions
A if this is the problem ,cps or rust or wiring, does this shut off the sparks or the fuel

B What is the ECM, is it the ECU?

Having asked questions both here and on A.M. owners club, it was suggested I see if it will run on easy start (just a bit) to see if ignition is ok

Obviously if it is a CPS problem its better its a replace sensor than a wiring problem i.m.o.

I wont be beside the car for four days yet

Thanks

rugbyman · 16-01-2019 5:07pm

By the way, changing he plugs is a ten hour job, eight if the mechanic has done it before

TeaBagMania · 16-01-2019 5:15pm

A. it shuts off the spark as the ECM\ECU dosen't know where the crank is, and it seems since you have fuel pressure on one side of the motor at least one of the fuel pumps is working.
Given the age of your Aston, if i have to drop the tank both pumps would get replaced

B. ECM = Engine Control Module, ECU= Engine Control Unit. Both the same thing. I think the new one is PCM = Powertrain Control Module

you might ask the guys over in the A.M. club if this is the correct part...
http://www.astonmartincarparts.com/part/astonmartin/db7-vantage/39-85756/sensor-crank-timing/150-653-23764-649783-178827.html

Skatedude · 18-01-2019 1:08pm

As mentioned, crank shaft position sensor, or possibly cam shaft position sensors.

Aston Martin DB7 won't start

Comments