Fuel Pump Relay Location

[Pat S]

'91 Q Intermittently will not start....cranks fine. Won't start. Pull fuel pump fuse....hear a "click" under dash (maybe one of the three blue relays next to fuses) Starts up and drives fine after relay "clicks".

History: Fuel pump replaced recently due to humming. Fuel pump control unit seems to operate fine....I did not wait for fuel pump to fail to replace pump.

Thanks

[Q45tech]

The fuel pump relay is in trunk [behind passengerside panel]

[trackfactory]

I have a similar problem on my 91 Q45 (No Active suspention).

When the pump started to hum, and finally quit, I replaced it. Shortly after, the intermitent starting problem occured. I found a pin on the pump module burned, and had to replace it as well.

2 years later (last week) I was splicing in the Mass Air flow sensor connector harness because the original one was cracked and falling apart, causing rough iddle and loss of power. I disconnected the battery terminal while splicing the connector in, and when I was finished, I had the symptom of cranking but no start.

I thought it was something I had done related to the air flow meter, and triple checked my work.

Upon further investigation I found that there was no gas flowing thourgh the fuel filter or the lines. I checked the 15 amp fuse under the dash (OK). I checked the three blue relays next to the fuse box under the dash (thinking one of them was the fule pump relay). The pump was not coming on, so I checked the moduled. I swaped the module out with one I had laying around.

Before I go out and purchase a pump, I would like to make sure the relay is good. From the reply to your post I now know that the relay is in the trunk, and not one of the three blue ones next to the fuse box under the dash.

Funny thing though, the pump did not exibit the typical sysmtoms of humming. I was wondering if something I did with the air flow meter connector harness could have caused the pump or the relay to go bad.

Anything you can offer will be helpful.

Thanks!

[texasoil]

maf not connected to fuel pump in ay way. Check the connections carefully on the plug to the fuel pump controller. fuel pump control modules have to be grounded to work

[Q45tech]

"When the pump started to hum, and finally quit, I replaced it. Shortly after, the intermitent starting problem occured. I found a pin on the pump module burned, and had to replace it as well. "........................"The pump was not coming on, so I checked the moduled. I swaped the module out with one I had laying around. " ?????????????????????

So you installed a used FPCU is that correct?

So using a jumper wire with alligator clips ground the pump terminal negative in the white molex connector .Change the GREEN fuel relay just for drill the over current may have pitted the contacts

[trackfactory]

Worked on the car all weekend. Found a wire from one of the leads on the MAF connector connected to body ground (dealers work). This in turn blew out the ECU. Once the ground wire was removed, the fuel systems started working again (pump, relay, FPCU). But it was too late, the ECU was already gone.

I was able to get an ECU from the junk yard for $150, but later found that the FPCU was also gone. I'm also thinking that the MAF might be damaged as well because my idle is a little low and rough. Car accelorates fine but at stop lights or in park, the idle is a little low and rough.

Thanks for all the help.

[Q451990]

The extra ground wire is a fairly common practice. The FPCU is a common issue when the fuel pump is pulling too much current and needs to be replaced. I'd say your low idle issue is related to a dirty intake and throttle body. Try setting the base idle up some (with the screw on the AAC valve) and see if that fixes it. It's not really a cure, but a good cover-up until you can get the plenum and TB off for a good cleaning.

Heath

[Q45tech]

The extra MAF ground was a fix for corroded grounds which tended to cause error in low flow MAF readings [at idle].

Installed when techs really didn't understand.

MAf really doesn't control idle speed, just tells ecu that air is flowing ----- so very inaccurate at idle speeds.The ecu has a recorded idle rpm 650-675 and tries via IAC and ignition advance to maintain [match] that speed...........when it can't without overextending IAC, changing injector open time, or changing timing by more than 3 degrees, it gives up as a warning to you [low idle speed] that other work must be done!

The ecu doesn't limit upper idle speed [too high an idle] caused by misadjusted IAC bypass or warm up or misadjusted throttle opening screws or a too tight throttle cable.

[trackfactory]

Thank you all for the invaluable info. I've gotten plenty of usefull info from this forum.

Very informative and helpfull.

PS, Since I went out and brought an after market Bosch fuel pump that wasn't needed, I have no use for it. If anyone knows of someone who needs one, please let me know.

The pump is still in the plasic inside the box! Paid $270 for it. I'm just looking to get (some) of my money back. I'll take $200.

Thanks again.

[Q45tech]

Why would you pay more for a low performance after market [which is not compatible exact current draw per rpm] than the oem cost from one of our parts sponors?Bosch USA/Europe is not the same company as BOSCH JAPAN, which bought the name and some designs after WWII.

[trackfactory]

Didn't know that! I guess I have to learn more about your parts sponsors.

[trackfactory]

My rough/low iddle problem has now shown new symptoms.

If the temperature falls below 60 degrees during the night, when I go to start the car up in the morning, she starts right up, but shuts right off. It takes about 10 to 12 tries to get it going. I can also smell a strong odor from the exhaust. Like it's too rich in gas.

I know that the guys that helped me work on the car previously, pulled out the spark plugs, and pulled out the crank angle sensor. Is it possible that the crank angle sensor is the culprit? Is the position of the crank angle sensor critical? I noticed that the holes for the bolts are slotted and you can turn the sensor on an axis.

I tried adjusting the air flow on the ACC, it brought the iddle rpms up a bit, but doesn't help with the hard starting in the morning.

I'm becoming increasingly frustrated with this car. When it runs good, I love it, but when there are problems, I feel like putting it through a crusher.

Any suggestions?

[trackfactory]

Rough iddle problem has gotten worse! It takes 15 minutes and about 20 tries to get the car going now.

The engine turns over and starts right up, then immediately dies as if starving for gas. I can smell a strong odor of gas coming from the exhaust.

After about 15 minutes of trying over and over again, the car will maintain rpm's and run fine. If I turn the car off for longer than 15 minutes, the problem comes back.

Replaced the MAF on the suggestion of a friend/mechanic. Didn't help one bit.

Please help! Any suggestions would be greatly appriciated.

[Q45tech]

THE CAS is critical as it is master clock for ecu!When it was removed was the timing [light against crank pully marks] set precisely [15 +- 2 degrees warmed up at 650 idle rpm].

Sure you don't have an air leak [hose netween MAF and TB] from messing around.

Why don't you take it to Vanmeter in S. Jersey, as you have been playing around for 6 weeks without resolution.

Really need the Consult to gather data on sensors.

[trackfactory]

Can you give me more info on Vanmeter in S. Jersey?

I'm affraid to take it back to the Infiniti dealer near me. They are not trust worthy.

Thanks.

[maxnix]

Keith Vanmeter Vanmeter Auto ServiceMantua New Jersey856-415-2022

[Jesda]

I'm adding Vanmeter to my list at Q45.org.

[tangalora]

This is an Infiniti mechanics' thread titled "fuel pump relay location" so I figured I'd post an old photo of the fuel pump relay location for a 1990 Infiniti Q45 (because it wasn't clear to me the first time I looked for it either) ... and because this photo will help the next poor soul who looks for the same relay next time; and because none of the fuel-pump-related nico threads seem to show a photo of the Q45 fuel pump relay location.

Going through my notes, the 90 Q45 fuel pump relay is the lime-green relay circled below in the passenger-side of the trunk behind the side fiberboard bulkhead (near the antenna motor).

A diagram similar to the photo below is located in the 90 factory shop manual on page EL-98 diagram SEL716N. A closeup of the relays in their bracket is shown on page EF & EC-168 diagram SEF614J. A shot of the whole Q45 showing the relay in the phantom view is on EL-155 diagram SEL761N.

Despite the fact that some folks said the blue relay next to the lime-green fuel pump relay is for the radio antenna motor, page EL-147, the second page of diagram SEL72N clearly marks that blue relay as the "Courtesy lamp relay (Blue)". (The power antenna timer is a larger box near those two relays according to that diagram.)

As are the diagrams of the fuel pump relay location, the procedure for checking the fuel pump relay are also splattered about. For example, page EF & EC-181 describes the testing of terminal 18 of the ECU to check the fuel pump relay; EF & EC-190 diagram ASEF054F gives the wiring diagram & continuity test for the fuel pump relay; and EF & EC-169 diagram SEF618J shows the test for the harness connector to the fuel pump relay.

I've been told these relays (being mechanical beasts) almost never go bad, but, they're cheap enough to replace.

I snapped hundreds of photos when I followed Nico instructions for a 1990 Infiniti Q45 fuel pump & fuel pump control unit remove, repair, & replacement procedure ... it's too bad I never had the time to write it all up in one complete article. The information for the entire process is scattered about Nico in a variety of threads, some of which are (in no particular order):

a) NICO Forums > Online Mechanic > Infiniti Online Mechanic > 1992 Q45 fuel pump modulator http://www.nissaninfiniticlub....=3984b) NICO Forums > Online Mechanic > Infiniti Online Mechanic > Installing Fuel Pump Control Module?? http://www.nissaninfiniticlub....36948c) NICO Forums > Online Mechanic > Infiniti Online Mechanic > problem after changing fuel pump [/http://www.nissaninfiniticlub....14348d) NICO Forums > Online Mechanic > Infiniti Online Mechanic > q45 fuel pump/control module http://www.nissaninfiniticlub....34503e) NICO Forums > Online Mechanic > Infiniti Online Mechanic > Fuel pump problem http://www.nissaninfiniticlub....11900f) NICO Forums > Online Mechanic > Infiniti Online Mechanic > feul pump control unit (sic) http://www.nissaninfiniticlub....18148g) NICO Forums > Online Mechanic > Infiniti Online Mechanic > Fuel Pump Replacement http://www.nissaninfiniticlub....=6268h) NICO Forums > Online Mechanic > Infiniti Online Mechanic > Fuel pump http://www.nissaninfiniticlub....47728i) NICO Forums > Online Mechanic > Infiniti Online Mechanic > q45 fuel pump controller http://www.nissaninfiniticlub....73822j) NICO Forums > NICO General > Infiniti General > Fuel Pump Pictures http://www.nissaninfiniticlub....d=454k) NICO Forums > NICO General > Infiniti General > Q45 fuel pump modulator http://www.nissaninfiniticlub....13588