JustJeff

iTrader: (13)

I'm trying to work on my fathers 91 convertible. It won't turn over and is acting like it isn't getting fuel. Here's what I've tested so far:

1. Spark plug wires all getting spark
2. Engine fuse (15A) is good
3. EGI fuse is good
4. Fuel pump operates when it's jumpered
5. I have continuity on pump harness at A and C
6. Fuel pump resistor relay is seeing resistance. The only pins that are slightly off is E-F and it's seeing 1.1ohms rather than .7-.9. I doubt that .2 ohms is enough to throw off voltage but someone who knows better please post.
7. I've checked voltage at fuel pump harness. All the measurements are jumping around quite a bit (possibly my choice in grounding point, trunk floor?) BUT I'm not sure which pin I'm looking for 12V on. Only one that is in 12V range is pin D and it ranges around 13-11V but mostly stays in 12V range. I plan on checking voltage more once I've gotten my spare wiring from another location and simply run a ground wire from battery post to trunk of the car.

I swapped a known good fuel pump and I have a new fuel filter ready to put on if needed. I've thought it was electrical because all the sudden the car wouldn't turn over and so far as I know (I don't drive it) has been driving fine. What are symptoms of a clogged fuel filter? Will they suddenly say, "nope"?

j9fd3s

iTrader: (3)

when you jump the fuel pump does it run?

if you have spark the CAS is working, and the ECU is on, so you SHOULD be getting injector firing as well.

so if you jump the fuel pump and it doesn't run, per subsection 12A of the memorandum #6912, section A, i must ask if there is gas in the tank.

does the fuel pump actually output any fuel.

JustJeff

iTrader: (13)

LOL, yes fuel in the tank.
Yes, fuel pump does operate when it is jumpered (see first post)
Yes pump is outputting fuel. I had hoses off and jumpered...a mess was made. But I do not have access to any tools to see what kind of pressure its creating.

A couple of other things:
I can try to turn the car over to the point of thinking it would be flooding....no smell of gggas.

JustJeff

iTrader: (13)

Posting from smartphone is pissing me off. I'll add more when I get home.

RXSpeed16

iTrader: (41)

Are the fuel lines backwards?
Was this a sudden problem or was it sitting a while?

JustJeff

iTrader: (13)

Ok, now that I"m at a computer...

I cranked on the engine some and directly after I pulled the return line off and had no pressure, no nothing no fuel in the line at all. I don't know enough to know if that is normal behavior given that the engine never turned over. My other thought is that perhaps the fuel filter is clogged and fuel is never getting to the engine and thus never returning to the tank.

JustJeff

iTrader: (13)

Fuel lines are correct. The car very well may have sat for a week or so without being driven, but it not turning over was/is sudden in that it never had trouble turning over before.

JustJeff

iTrader: (13)

Bumping this for a little help....though I may simply pop the new fuel filter on and see what happens

j9fd3s

iTrader: (3)

if you have spark, you <should> have working injectors, so then it would have to be a physical fuel delivery problem

RXSpeed16

iTrader: (41)

^Like he said, does it start if you jumper the pump check connector?

The pump should run when you turn the key to 'start'. The fact that your return line was dry after cranking indicates this is not happening.

It could be the rubber hose in the fuel pump assembly that connects the pump to the hardline. Filters don't usually just completely quit unless part of it breaks off. Even then, complete blockage is unlikely.

JustJeff

iTrader: (13)

I just swapped the fuel filter and no change. One thing to note, there was no fuel after the fuel filter, but there was fuel pre-filter.

I'm thinking this has got to be a voltage problem. Low voltage to the pump so the pump isn't creating enough pressure for the fuel to get through the filter. Guess I'll get my meter out and figure out which pin on pump harness is supposed to be seeing 12V.

edit:

I tried starting the engine while fuel pump was jumpered and got no change.

Also I removed the jumper and pulled the fuel hose feeding the engine (post filter) and got a nice bath of fuel. Could it be something not to do directly with fuel? Could it an AFM/MAF? I'm going to save voltage testing for tomorrow before or after class.

satch

iTrader: (1)

Test the Brown/White wire at the TPS. This is the Vref voltage sent to other sensors, AFM included. Should read 4.5 to 5.5 volts w/key to on. If it is rather low then it's shorting out (AFM would be the likely source). Also, if the voltage checks out you know the ECU is powered correctly.

And the fuel relay could be bypassed by jumping a Blue/Red wire to a Blue/Green wire.

jjwalker

I had an issue with my car and a clogged fuel sock. I got fuel pressure into the rail, but it wasn't enough to run the car.

I too, also didn't smell gas when I feverishly tried to start the car over and over again.

JustJeff

iTrader: (13)

I'll check tomorrow, whenever I can find the time.

I don't think it's the sock. I swapped the fuel pump and the exterior of the sock looked fine.

clokker

iTrader: (2)

If possible, the simplest test would be fuel pressure right after the filter.
Should be 90 psi or so.
If it is, you know the pump, wiring, fuel line and filter are all good and the problem is on the intake.

jjwalker

Mine didn't look clogged either.

JustJeff

iTrader: (13)

I may be buying a tester later today. It's probably one of those tools I should have but up until now hadn't had any reason to own one.

I'm curious how you knew to clean it and what you used to clean it?

j9fd3s

iTrader: (3)

if you spray your choice of flammable aerosol into the intake does it fire and then die? if yes, then keep looking at fuel, if no then you have something else going on

clokker

iTrader: (2)

Axe body spray?

jjwalker

I just replaced it. That was years ago, so I don't remember what I paid, but it was cheap.

j9fd3s

iTrader: (3)

lmao, i wonder if that works?

JustJeff

iTrader: (13)

OMG!! Imagine how many chicks a car would pull if I was able to incorporate axe body spray into my fuel system!?!?! And going further down this rabbit hole, why has Axe not started selling body spray scented air "fresheners" to teens?? Your crap car can instantly do this:


For the record, I'm actually tempted to buy some Axe just to see if the awesomeness of Axe can temporarily start the car??

JustJeff

iTrader: (13)

Brown/White wire shows 5V

By fuel relay you mean the resistor relay in front of the air filter correct? Or do you mean the relay that is under the dash?

I did do a resistance test on the resistor relay and it showed 1.1ohms (probably K ohms, but I don't have the FSM in front of me). Either way specs in FSM was something like .7-.9ohms. You think .2 ohms is enough to lower voltage enough to effect the fuel pump? I only know enough about electrical principles to be dangerous. From my reading, fuel pump should be seeing 12v and if the resistor relay or wiring is faulty it will drop voltage below 12v and to dangerously low levels. How does amperage play into this? If I apply Ohms Law to my assumed voltage of 12 with a resistance of .9 (high end of FSM range)
12/.9=13.3A

Using the resistance I found of 1.1
12/1.1=10.91A

All this math is very speculative in that I'm assuming 12v. I guess I could check the voltage on the same pins I checked resistance. But again that is all assuming that the voltage doesn't encounter any loads between that point and the pump. On top of that I don't understand the role of amperage in this whole thing....so really I guess I did all of this to amuse myself?

Curious about how I do the pressure test. Do I simply jumper the fuel pump and see what pressure I have. Or do I want a helper trying to turn the engine?

I did one test with the fuel pump jumpered. I took my reading where the fuel line feeds into the spider's nest. I only saw 60psi, BUT I also had a little bit of a leak that was spraying a nice mist of fuel. I'm curious how much that leak contributed to less than 90 psi..and if 90 psi is even what I'm looking for with the pump jumpered.

I'm letting the pressure die down some before changing how I'm putting the tester inline with the fuel hose. See if I can't get this leak worked out and retest.

JustJeff

iTrader: (13)

Alright, test fuel pressure with no leaks (plumbers tap on screw fittings do wonders)

With fuel pump jumpered: 65psi
No jumper and trying to turn the engine over: 60psi
Now granted I did not check pressure right off the fuel filter. I checked at the output from fuel filter to rats nest. I doubt that 1ft of vertical hose is enough to drop 30 psi.

All that being said, I checked my Haynes and ti's showing EGI fuel pump pressure (I'm assuming they mean N/A, because turbo is listed below it) it shows 64-85.3psi

and hold pressure of 57psi

I checked voltage at the fuel pump with the pump jumpered. The only pin in that range (D IIRC) showed a solid 12v

welfare

what did the plugs look like when you pulled them? have fuel on them? you can check for injector pulse with a 194 bulb. peel the tangs down on the bulb. disconnect a primary injector. insert the tangs into the connector and crank the engine. see if the bulb flashes.

TBH, i think the testing is getting a bit scattered here though. a diagnostic flow chart is the most efficient way to find the problem.
start at the top. determining whether the problem is fuel or ignition related.
if you pull the plugs and they look dry, i would do as mentioned and fog in a shot of propane while someone cranks. if it fires briefly, go after fuel. if not, ignition. you have ignition when pulling the plug and grounding it. but do you have the voltage it requires to overcome engine compression? there's a huge difference between ignition inside an engine and ignition in atmosphere. an HEI tester of the specified resistance is the quickest, easiest and cheapest way to confirm