[oliver_human]

I need some technical and/or spiritual help.
I'm not normally superstitious but thinking maybe it would help if I was.

I have a 1994 Vitara with a G16B engine, bought cheap from a friend as it was sitting around for 2 years.
Have replaced or fixed many things, that I will outline below. The problem that persists now is a really hard one to diagnose as it only shows itself on hot days (I'm in Darwin) or after driving for about an hour. Its like the fuel pump is cutting out, at first momentarally, then as I keep driving, all power will be lost for a few seconds, then for increasingly long periods at increasing frequencies until I have to pull over. Engine always idles sweetly, and flat spots are more intense when accelerating. If the engine is turned off for an hour or so, we get a brief reprieve before problems start again.

This is interesting: I have bypassed the fuel pump relay and measured voltage between positive pump supply and earth. Results: when we have an engine power loss incident, I see a voltage rise (from 12.5 v while running to 13.5 volts when stalled for a few seconds). I have not been able to measure current but can only assume that the fuel pump is somehow losing power. I cant really see how this is possible.

Things done so far:
* new fuel pump
* new fuel filter
* cleaned fuel tank
* cleaned fuel lines
* cleaned and pressure checked injectors
* checked MAF sensor
* new ECU temp sensor (this was suggested by auto elec)
* some other things

The engine runs pretty sweetly otherwise, and even when it is having problems, it always idles nice.

Would love to hear some suggestions from you Suzuki enthusiasts out there.

Oliver

[missmyljdaze]

Dunno about the hot days bit, but after an hours driving it might be from a vacuum building up in the fuel tank from a blocked or crushed breather line?
When the fault shows up next, take off the fuel cap and see what happens.

Maybe emission control stuff is full of gunk??

When you cleaned the fuel lines and tank did you find any charcoal??

We had a similar fault to yours in my son's hyundai - charcoal canister has a flimsy bit of foam to hold the charcoal pellets in place, after years of being overfilled the foam had degraded and broken up - allowing bits of charcoal to migrate throughout the entire fuel system.
Blew out all the lines, drained and cleaned out the tank, did a dodgy temporary fix by cutting open the canister and jamming fine stainless steel mesh in to keep the charcoal in place, then welded the plastic canister back together.
Hyundai ran like a dream [until son wrote it off]

[alien]

Coil packs or leads IMO.

Does it feel like it drops all 4 cylinders or just 1 or 2?

It could also be a bad earth?

[fordem]

oliver_human wrote:

This is interesting: I have bypassed the fuel pump relay and measured voltage between positive pump supply and earth. Results: when we have an engine power loss incident, I see a voltage rise (from 12.5 v while running to 13.5 volts when stalled for a few seconds). I have not been able to measure current but can only assume that the fuel pump is somehow losing power. I cant really see how this is possible.

Where exactly was this measurement taken - from the rise in voltage, it can be deduced that the current flow stops, and that means the circuit is being interrupted at some point downstream from where you're making the measurement, or as was suggested in another post, in the return, which is the "earth" or chassis ground - repeat this measurement as close as you can to the pump itself - if you see the same rise in voltage, the fault is still downstream from the measurement point, so you will have eliminated the feed wiring as a possible cause.

You can also measure the voltage drop on the chassis side of the wiring - meter negative to a known good ground, meter positive to the ground wire coming out of the pump connector - it should be close to zero with the pump running, and stay there at all times, if the connection is good - if you see more than a few tenths of a volt, you have a bad ground connection, and if it jumps up higher when the power loss occurs, you've found the cause.

[sideways]

I'd also be looking at the ignition. A new coil and ignition module as about $40 on ebay, handy as spares at the very least.

I'd be fitting a fuel pressure gauge to confirm/deny the problem. You can tee in a cheap oil pressure gauge to do the job. Chasing voltages will give you a maybe but you know if you still have good fuel pressure the problem isn't there.

[barbender]

I had the exact same problems with a Hyundai Excel a quite a few years ago, it turned out to be the crank angle sensor, don't know if the Vitara has a crank angle sensor, if so it might be worth a try. I checked on the net when I was having the problem and a easy diagnosis was to pour very cold water on the sensor when the problem arose and it gave a temporary (even though short) fix, more of a way to diagnose the issue. Google crank angle sensor problems and issues and diagnosis on the WEB, hope this helps, regards

[oliver_human]

Thanks for all your ideas chaps. I will do some more investigating and report back. Think Ill start with Fordem's suggestion and check out the pump wiring first. It baffles me that it would only show a fault after 1 hour. Doesnt sound like a bad earth or loose wire, but have a look...

[barbender]

Re the crank angle sensor, I never had the problem from cold only when the engine was hot usually anywhere from half to one and a half hours of driving, regards

[bob_oz]

fuel pumps overheat when old,

symptoms are loss of power after a time, feels like progressively loosing throttle to a point where it will struggle to idle.
cuts out progressivly until you're stuck being able to idle and not much more.
letting it sit off for a while helps it cool down and you're off again for a while then back into symptoms
I'd get 1-1.5h into driving and it would start to fail - uphill or heavier throttle usage like 110kmh would cause it to come on sooner.

the fuel pump electric motor windings get old and as they overheat they increase resistance, limiting current and power.

Mine was doubly screwed as the internal filter was rotten with debris which didn't help.

I threw a second hand pump in and was right as rain.

[Gwagensteve]

I don't know how an in-tank swimmer pump could "overheat" - It's cooled by the fuel. The pump would gave to be getting so hot and adding so much heat to the fuel the tank would be noticeably hot and/or the fuel pump fuse would blow.

I'm not doubting you were having problems with the fuel pump but the problem with an electric motor ill be it goes open circuit, not high resistance.

I'm sure the real cause in your case was the debris clogging the pickup, reducing fuel pressure when you're placing it under high demand - "uphill or heavier throttle usage" is the clue. EFI fuel pumps aren't designed to lift, which is another way of saying "work against an inlet restriction"

In the case of the OP, I'm pretty sure the problem will be with the ignition side. Coil/igniter/leads.

[oliver_human]

barbender, the crank angle sensor is inside the distributor on this model I think. Distributor all seems fine.

bob_oz, the fuel pump is brand new - see jobs ive done above

Gwagensteve, I have tried another coil, no change. Dont think its the leads as it runs steady and when it cuts out we lose all cylinders. I did check the igniter with the test in the book and it was fine. But would you think it could still be the problem?

Ill try anything, but dont just want to replace things willy nilly - as mechanics do - without a good reason.

[fordem]

First post says the fuel pump was replaced ...

Of note is the fact that voltage to the pump feed increases, because that suggests the load decreases, and does point to the pump shutting off.

[Gwagensteve]

I'm not sure that's conclusive, because the fuel pump relay was bypassed. All that shows is that when the engine coughs total electrical load drops.

My understanding of EFI computers is that if the ignition cuts out the fuel pump is shutoff, to prevent a fire

[bob_oz]

Gwagensteve wrote:

I don't know how an in-tank swimmer pump could "overheat" - It's cooled by the fuel. The pump would gave to be getting so hot and adding so much heat to the fuel the tank would be noticeably hot and/or the fuel pump fuse would blow.

I'm not doubting you were having problems with the fuel pump but the problem with an electric motor ill be it goes open circuit, not high resistance.

I'm sure the real cause in your case was the debris clogging the pickup, reducing fuel pressure when you're placing it under high demand - "uphill or heavier throttle usage" is the clue. EFI fuel pumps aren't designed to lift, which is another way of saying "work against an inlet restriction".

Ah yes - re-scanned and saw the line re replacement pump - my bad

Yeah nah, the tank was spotlessly clean - debris was inside the tank filter from past driving over years downstream from the pump - something that wasn't great and would have put the pump under load but no where enough to kill a normally functioning pump.

Uphill requires more throttle and more fuel, will show a low or failing fuel pressure issue more readily and long before you throw a fuel pressure low code.

In tank pumps still overheat easily when they get old, most are inside the plastic filter - pump housings aren't great at dissipating heat as they are a metal/plastic/resin can, when they overheat it's typically from the winding being old and having a higher than normal resistance - the increased resistance dumps more heat off the winding into the housing further increasing the resistance as the copper heats up, this increasing resistance drops the voltage able to get through reducing the pump power - open circuit is when the winding burns out and there is a break, in this case she's dead permanently.

[Reubs]

Sounds similar to a problem I had. Replaced fuel pump before realising the actual problem was the contacts in the OEM loom for the fuel pump on top if the tank. Contacts would open after heating from poor contact. Replaced with a couple of quick crimps and problem solved for last 5 years or so.

[oliver_human]

Good idea Reubs.
I tried this yesterday. REplaced connectors with crimps and went for a drive. 45 min down the road problem started again and I said "Damn it."
While driving home I checked voltage at pump supply positive next to tank with a long bit of wire to a voltmeter on the passenger seat, after fordem's suggestion. Volt drop as before.
So ... Problem must be at tank connections, or earth wire, or pump connections in tank?
Does anyone know where fuel pump is earthed ouside the tank?
I will eliminate possibility by bypassing earth to cables on top of tank before I pull the tank for the 3rd time.
Any other diagnostic ideas from you blokes before I do this?

[Gwagensteve]

Is voltage maintained at the pump the whole time, including during the "cough"?
Does voltage at the pump increase from 12.5V (this seem s a little low) to 13.5V during the cough?

I think you need to confirm amp flow in the pump circuit. I don't have my own car in state I can readily confirm this ATM, but putting a clamp meter on the fuel pump feed should show some amp flow. If volts remain at the pump circuit the whole time during the cough but the amps drop in line with the volt rise you've confirmed the pump is turning off for whatever reason.

Confirm your results by hooking the volt meter between the +ve and -ve terminals on the top of the tank, not another earth in the car somewhere. If you have a faulty earth, volts will drop to zero. with the measurement being taken between the +ve terminal on the tank and another earth elsewhere, you can't confirm an earth failure.

[oliver_human]

Sorry to bring this up again. I had another look at this vehicle the other day after a break.
Have found no wiring faults at all, but volt drop problem persists, so maybe it is just that the load on the pump is dropping suddenly due to fuel vaporisation in the delivery lines?
This seems plausible now because last time I had a long drive on a hot day the car was barely driveable, but a storm came over, air temp dropped very quickly and we got all power back.
I have taken injectors off and notice signs of leakage past the o-rings. Dont know how this could be part of the problem butI will put a new injector seal kit in tomorrow.

Does anyone think this is the likely cause? And can suggest a cure?

Oliver