Fuel pump not priming.
Discussion
Good morning gents, my 1998 400 has been stood for about a month and now won't start. The fuel pump is not priming although immobiliser seems to be going through its sequence. I have checked fuel pump and connections are clean and tight but no voltage present when fob is pressed. Giving the pump a tap has made no difference either. I have disconnected the battery to see if a reset would do anything but no joy with that either. The relay connections are also clean and tight. I am now stuck so would appreciate what to do next. Many thanks.
You say immobiliser appears to be going through the motions, so I assume you can crank but no fuel?
I assume alarm fob has re-synced ok after reset and you can lock/unlock from the fob ok?
Obvious checks, fuses & fuel/ecu relay in the footwell spaghetti, assuming fuses ok and voltages ok at relay outputs, only leaves broken 12v feed to fuel pump or immobiliser fubared.
You could try the thump the dash underside on passender side near transmission tunnel whilst cranking trick to see if it is just a sticky immobiliser relay, failing that run 12v direct to the pump and see if you can start it
I assume alarm fob has re-synced ok after reset and you can lock/unlock from the fob ok?
Obvious checks, fuses & fuel/ecu relay in the footwell spaghetti, assuming fuses ok and voltages ok at relay outputs, only leaves broken 12v feed to fuel pump or immobiliser fubared.
You could try the thump the dash underside on passender side near transmission tunnel whilst cranking trick to see if it is just a sticky immobiliser relay, failing that run 12v direct to the pump and see if you can start it
Edited by ukdj on Wednesday 18th February 13:12
Listen for the ECU relays in the passenger footwell as you turn on the ignition (dont start) - two close together (main and fuel pump) with a clear click- then about 2 second later the fuel pump relay should drop out, again with a click. This will at least prove the ECU is doing its thing to switch the pump on.
Do the relays have a metal body possibly with a red stripe?
if so they are probably getting on a bit, worth replacing them both for new ones.
New ones will probably be brown plastic body, bosch part no: 0 332 014 112
Worth checking the wiring to the relay sockets to make sure it isnt a dodgy connection there too.
if so they are probably getting on a bit, worth replacing them both for new ones.
New ones will probably be brown plastic body, bosch part no: 0 332 014 112
Worth checking the wiring to the relay sockets to make sure it isnt a dodgy connection there too.
Edited by ukdj on Wednesday 18th February 18:24
I was always taught... "You can't fix something until you understand how it works" 
Keep in mind the immobiliser is just a switch, one you turn on & off with your fob from a distance, but a switch all the same.
Actually it's two switches.
One switch opens the circuit to the starter solenoid, so when you turn the key to the sprung start position you can crank the engine.
The second switch turns on the ECU, and its actually the ECU that turns the fuel pump on not the immobiliser but clearly it's all linked in a chain if you like.
The ECU will only turn the fuel pump on for three seconds when you turn the ignition on. After three seconds the ECU turns the fuel pump off because obviously you don't need a flow of fuel until the engine is running, the three second pulse is just designed to prime the fuel rail in preparation for the start.
The ECU wont turn the pump back on again until it either sees an RPM signal from the distributor indicating cranking, or you turn the ignition off & back on again.
Relays are just electromechanical switches (mini solenoids if you like) that allows a low amp feed to switch on a high amp circuit, they are used to protect low amp switch contacts that wouldn't ordinary cope with the higher amp demands of components like fuel pumps, starter motor solenoids, headlights, horns ect ect.
The ECU has a relay and the ECU activates the second relay on the fuel pump circuit, if your fuel pump relay is faulty obviously the fuel pump wont run, if you then put that faulty fuel pump relay in the ECU relay socket the ECU wont switch on. And because the ECU isn't live it can't turn the fuel pump on.
So you see, the often promoted practice of swapping the two relays around is the answer to nothing other than further confusion!
The truth is the problem may be a relay, or it may reside inside the immobiliser which itself houses two small low amp switching relays, one for each of the two circuits it controls (ECU & Stater Motor Solenoid).
So how do you know where the problem really is without blindly replacing things at great cost in the hope you might stumble on the solution?
Well here's a clue....
Keep in mind the immobiliser is just a switch, one you turn on & off with your fob from a distance, but a switch all the same.
Actually it's two switches.
One switch opens the circuit to the starter solenoid, so when you turn the key to the sprung start position you can crank the engine.
The second switch turns on the ECU, and its actually the ECU that turns the fuel pump on not the immobiliser but clearly it's all linked in a chain if you like.
The ECU will only turn the fuel pump on for three seconds when you turn the ignition on. After three seconds the ECU turns the fuel pump off because obviously you don't need a flow of fuel until the engine is running, the three second pulse is just designed to prime the fuel rail in preparation for the start.
The ECU wont turn the pump back on again until it either sees an RPM signal from the distributor indicating cranking, or you turn the ignition off & back on again.
Relays are just electromechanical switches (mini solenoids if you like) that allows a low amp feed to switch on a high amp circuit, they are used to protect low amp switch contacts that wouldn't ordinary cope with the higher amp demands of components like fuel pumps, starter motor solenoids, headlights, horns ect ect.
The ECU has a relay and the ECU activates the second relay on the fuel pump circuit, if your fuel pump relay is faulty obviously the fuel pump wont run, if you then put that faulty fuel pump relay in the ECU relay socket the ECU wont switch on. And because the ECU isn't live it can't turn the fuel pump on.
So you see, the often promoted practice of swapping the two relays around is the answer to nothing other than further confusion!
The truth is the problem may be a relay, or it may reside inside the immobiliser which itself houses two small low amp switching relays, one for each of the two circuits it controls (ECU & Stater Motor Solenoid).
So how do you know where the problem really is without blindly replacing things at great cost in the hope you might stumble on the solution?
Well here's a clue....
Edited by ChimpOnGas on Wednesday 18th February 20:01
Yes they are the metal ones with a red stripe. Well Chimp, what can I say great answer, never seen the operation wrote down like that in plain English and easy to understand. Thanks, that I will save in my history file. So assuming there is a relay problem within the immobiliser, what is the answer? Can it be repaired or replaced or is it a case of fitting a different one and ripping the Metec out.
threespins said:
Yes they are the metal ones with a red stripe. Well Chimp, what can I say great answer, never seen the operation wrote down like that in plain English and easy to understand. Thanks, that I will save in my history file. So assuming there is a relay problem within the immobiliser, what is the answer? Can it be repaired or replaced or is it a case of fitting a different one and ripping the Metec out.
This every time....... 
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
threespins said:
Yes they are the metal ones with a red stripe. Well Chimp, what can I say great answer, never seen the operation wrote down like that in plain English and easy to understand. Thanks, that I will save in my history file. So assuming there is a relay problem within the immobiliser, what is the answer? Can it be repaired or replaced or is it a case of fitting a different one and ripping the Metec out.
Basically you have three choices:1. Best but costly - Full security system replacement Karl Baker or David at HF Solutions
http://www.hf-solutions.co.uk/
2. Still a good option but cheaper & DIY - Replacement TVR immobiliser kit from Abacus Alarms
http://www.abacuscaralarms.co.uk/tvr-alarms.html
3. Cheap and effective DIY - Bypass the immobiliser yourself which is easy, costs nothing and will solve the problem
But before you get into all this you need to use your multimeter to trace where the problem truly is so you're only replacing the faulty component not blindly replacing things in the hope you might stumble on the solution.
The problem could be the immobiliser or it could be a relay, these are the two most likely culprits, but it could also be the live feed to the fuel pump.
The fuel pump wiring TVR gave us was pretty poor and the spade connector at the pump gets covered in salt spray & road crud.
In fear of stating the obvious....."Have you checked your fuel pump fuse yet"
Start with the basics before you jump to the immobiliser
Good luck with it
Test the relays rather than just replacing them.
They may well be functioning perfectly in which case you will be wasting time and money.
Use a multimeter to trace the fault, not guess work.
That's the right way to fix things, faster and cheaper too!
They may well be functioning perfectly in which case you will be wasting time and money.
Use a multimeter to trace the fault, not guess work.
That's the right way to fix things, faster and cheaper too!
Edited by ChimpOnGas on Thursday 19th February 11:38
threespins said:
Many thanks, trouble is I'm as deaf as a post so would not hear the relays. Anyway swopped the two relays round and although it took about four attempts it eventually started. So any ideas, relay doesn't like being stood in a cold garage?!
This wouldn't work; the two relays are interlinked; only replacing them as a pair is a good practice. My guess is that one of them was a bit sticky, have had this happen a few times on cars that have stood for a while.
threespins said:
I figure like Oldred V8S that it is a sticking relay, just seems to happen when car has been standing in winter. got two new relays coming tomorrow so will prove it one way or the other.
Well you can bring a horse to water and all that 
Fault diagnosis via part replacement - "Should have gone to KwickFit"
Bon Chance with the lucky dip methods, I guess you could get lucky.
Just remember if you do effect a fix, it will be down to luck not applied intelligence.
If you dont achieve victory you will have wasted time & money, but hey you could always keep going with the same system until you either....
A. Fall on the problem
Or
B. Run out of money
Sorry to be a stuck record but surely you'd be better of spending your money on a cheap multimeter and tracing the fault properly?
That's not to say I dont wish you all the best in your quest to fix your car, good luck with it.
Dave.
ChimpOnGas said:
I was always taught... "You can't fix something until you understand how it works"
Keep in mind the immobiliser is just a switch, one you turn on & off with your fob from a distance, but a switch all the same.
Actually it's two switches.
One switch opens the circuit to the starter solenoid, so when you turn the key to the sprung start position you can crank the engine.
The second switch turns on the ECU, and its actually the ECU that turns the fuel pump on not the immobiliser but clearly it's all linked in a chain if you like.
The ECU will only turn the fuel pump on for three seconds when you turn the ignition on. After three seconds the ECU turns the fuel pump off because obviously you don't need a flow of fuel until the engine is running, the three second pulse is just designed to prime the fuel rail in preparation for the start.
The ECU wont turn the pump back on again until it either sees an RPM signal from the distributor indicating cranking, or you turn the ignition off & back on again.
Relays are just electromechanical switches (mini solenoids if you like) that allows a low amp feed to switch on a high amp circuit, they are used to protect low amp switch contacts that wouldn't ordinary cope with the higher amp demands of components like fuel pumps, starter motor solenoids, headlights, horns ect ect.
The ECU has a relay and the ECU activates the second relay on the fuel pump circuit, if your fuel pump relay is faulty obviously the fuel pump wont run, if you then put that faulty fuel pump relay in the ECU relay socket the ECU wont switch on. And because the ECU isn't live it can't turn the fuel pump on.
So you see, the often promoted practice of swapping the two relays around is the answer to nothing other than further confusion!
The truth is the problem may be a relay, or it may reside inside the immobiliser which itself houses two small low amp switching relays, one for each of the two circuits it controls (ECU & Stater Motor Solenoid).
So how do you know where the problem really is without blindly replacing things at great cost in the hope you might stumble on the solution?
Well here's a clue....
Dave, would you explain this a bit further. I thought that the immobiliser was 3 switches and controlled three circuits, 1) Ignition, 2)Fuel pump 3) Starter solenoid.Keep in mind the immobiliser is just a switch, one you turn on & off with your fob from a distance, but a switch all the same.
Actually it's two switches.
One switch opens the circuit to the starter solenoid, so when you turn the key to the sprung start position you can crank the engine.
The second switch turns on the ECU, and its actually the ECU that turns the fuel pump on not the immobiliser but clearly it's all linked in a chain if you like.
The ECU will only turn the fuel pump on for three seconds when you turn the ignition on. After three seconds the ECU turns the fuel pump off because obviously you don't need a flow of fuel until the engine is running, the three second pulse is just designed to prime the fuel rail in preparation for the start.
The ECU wont turn the pump back on again until it either sees an RPM signal from the distributor indicating cranking, or you turn the ignition off & back on again.
Relays are just electromechanical switches (mini solenoids if you like) that allows a low amp feed to switch on a high amp circuit, they are used to protect low amp switch contacts that wouldn't ordinary cope with the higher amp demands of components like fuel pumps, starter motor solenoids, headlights, horns ect ect.
The ECU has a relay and the ECU activates the second relay on the fuel pump circuit, if your fuel pump relay is faulty obviously the fuel pump wont run, if you then put that faulty fuel pump relay in the ECU relay socket the ECU wont switch on. And because the ECU isn't live it can't turn the fuel pump on.
So you see, the often promoted practice of swapping the two relays around is the answer to nothing other than further confusion!
The truth is the problem may be a relay, or it may reside inside the immobiliser which itself houses two small low amp switching relays, one for each of the two circuits it controls (ECU & Stater Motor Solenoid).
So how do you know where the problem really is without blindly replacing things at great cost in the hope you might stumble on the solution?
Well here's a clue....
Edited by ChimpOnGas on Wednesday 18th February 20:01
Haven't quite got my head around this yet!
Hi Chimpongas, I agree with everything you say. I do have an engineering background and have several multimeters. I just thought that as the relays were 16 years old and playing about with them got the car going then it would be prudent to change them for what little money they cost. They are now changed so I will report back after giving it some time without further trouble.
threespins said:
Hi Chimpongas, I agree with everything you say. I do have an engineering background and have several multimeters. I just thought that as the relays were 16 years old and playing about with them got the car going then it would be prudent to change them for what little money they cost. They are now changed so I will report back after giving it some time without further trouble.
Good luck, I hope the relays solve the problem.If you need to bypass the immobiliser give me a shout, the bypass is a free option to get you out of trouble, it will work but TBH there are more complete solutions out there and the price is coming down if you dont mind a bit of light DIY.
Although I've not used them myself Abacus Alarms offer a Meta TVR kit which looks like a good cost effective fix.
http://www.abacuscaralarms.co.uk/re-coding-meta-al...
Interestingly Abacus Alarms now have a statement on their website that pretty much mirrors what I've been saying for years..
Here's what Abacus say about the infamous "Hot Start Issue".....
The M36T2 immobiliser is a two circuit Thatcham approved immobiliser, it is manufactured with very high quality components to a very high standard & as such this is one of the most reliable immobilisers manufactured today, many of these systems are still working perfectly on vehicles which are well over 15 years age.
The problem, relay 1 (circuit 1) of the immobiliser can handle a maximum of 10 Amps, relay 2 (circuit 2) can handle 25 Amps.
Here's the rub, TVR have wired these circuits the wrong way around, the TVR fuel pump circuit goes through the higher rated relay 2, while relay 1 (rated 10A) has to handle the starter circuit. All being well there are no problems even though the two relays are wired the wrong way around, as testified in that they've been functioning perfectly for 10 years or more.
Problems arise when the starter solenoid begins to wear, in so doing it demands more & more power to function, when the current flow to the starter gets to the 10 Amp limit of relay(1) problems start, this gets exasperated when the engine is hot which in turn makes the solenoid hot which in turn requires even more power, I understand this is known as the hot start problem, this demand for power will eventually burn out the smaller relay.
Adding an extra 'hot start' relay to this circuit is not a permanent fix, this circuit will just demand more power which could eventually burn out the ignition switch or associated wiring to eventually the failure of the starter itself. Before this happens we recommend to have the solenoid/starter inspected & have it repaired or replaced if found faulty.
All replacement TVR adapted M36T2 immobiliser will now be sent out with the immobiliser circuits switched to match the TVR wiring, this will now match the higher rated relay to the starter circuit of the TVR, this should cut down on the hot start issue.
Add the "Hot Start Kit" if you like, but as I've been saying for a long time now... if that little switching relay burried inside your Meta unit is already burnt out adding in another relay (which is all the hot start kit is) isn't going to help you.
This is also why if you already have a "Hot Start Kit" and then go to Carl Baker or David at HF Solutions one of the first things they'll do is rip it out.
The ignition switch needs a relay sure, and TVR never fitted one
... but adding a relay (the hot start kit) to solve TVR's back-to-front wiring of the Meta unit is not really a proper permanent solution for anything.threespins said:
That made me laugh Chimp, just about sums up the phrase "they all do that Sir"
Great information though, learning more each day from you.
How does the alarm fit into all this, is it totally separate and just to do with locking the car?
No, the alarm unit under the dash is paired with the immobiliser hidden behind the radio panel.Great information though, learning more each day from you.
How does the alarm fit into all this, is it totally separate and just to do with locking the car?
And before anyone bleats on about a security risk by me revealing the location of these units it's all freely available information already out there on the interweb, including photos and instructions published on the Abacus Alarms website.
The two units are synced together and talk to each other, all be it in a crude way.
But basically you're on the right track, the alarm is mostly responsible for the locking & unlocking function, while the immobiliser simply deals with the activation and deactivation of the following two circuits.
1. The ECU and so the fuel pump
2. The starter solenoid via the sprung start position on the ignition switch
It doesn't take a genius to bypass the immobiliser on one or both of these circuits, 15 minutes to take the dash top off, 5 minutes locating the two key wires with a multimeter, add some basic logic and jobs a good'un.
But that's effectively a "hot wire" start, so I'll leave it there or the Nanny State TVR community will be all over me like rash
The truth is my 8 year old nephew could nick a Chimaera within a few minutes, if a professional car thief wanted to have it away with your TVR we're talking seconds not minutes.
Fortunately TVRs are not on their shopping list
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