Landcruiser fuel injection relay problem

For a long time now my 1992 Landcruiser has had an intermittent hot start problem. If the vehicle is at operating temperature and is shut
off it usually won't start for the next approximately 10 minutes. Very irritating when running errands, etc., but otherwise not much of a problem. Besides living with it and trying a few things I've have localized the problem to hot failure of the main fuel injector relay.
When it isn't going to start the "check engine" light doesn't come on as you turn the key and this fact coupled with the wiring diagram led me to changing the main EFI relay. Initially all seemed fixed but then the problem reoccurred. For whatever reason I eventually tried putting back in the original old EFI relay which was cold and it immediately started. I now have three of these that I swap as needed.
The problem seems to be overheating of the relay which causes a temporary failure. They actually get too hot to hold. Everything else about the vehicle's starting/running seems totally normal and I have owned it since new. This has been going on (off and on) for 2 years but is quite a bit less of a problem in the winter. I only use the vehicle intermittently so I've been reluctant to spend the money to get it checked out thoroughly though it would be nice to have fixed.
Any thoughts on a possible cause. I have speculated that the relay is getting too much juice but I really can't figure out how that would be and everything else be normal. Also the rest of the items in the relay/fuse box (which is under the hood) don't seem to be overly hot, just the EFI relay. Thanks in advance for any ideas.
Scott
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Scott wrote:

You can check the schematic if you can find one, but is is probably a resistance problem on the load side of the relay. Depending on it's design, (SPST, DPDT, ect.,) Whatever it controls on the load side(s) is pulling too many amps. That is why it is heating up so much. Check the fuse in the circuit and make sure it is of the correct amperage according to the fuse holder or owners manual. If it's getting as hot as you say, I would think that a fuse would be blown and the circuit opened, and obviously that is not happening since it runs. Check the terminal ends into the socket for corrosion and good contact. After fifteen years, it could be that.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The EFI relay may be protected by a self-resetting circuit breaker that resets (basically a bimetallic switch) when it cools. There was a similar problem with earlier generation Land Cruisers that was caused by a chafed wire behind the plastic trim panel on the driver's side of the cargo area, but I don't know if this the case here.
--

Ray O
(correct punctuation to reply)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks Ph@Boy and Ray. I can't find any obvious corrosion and I haven't had any blown fuses and in fact they are all still the original fuses. I am going to treat the vehicle-side female contacts regardless. What I can't figure out, among other things, is why it doesn't fail while running. It isn't beause it heats up under the hood after shutdown because it will fail to start within seconds of shutting it down. I'll keep plugging.
Scott
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
and Ray. I can't find any obvious corrosion and I

Keep us posted and good luck!
--

Ray O
(correct punctuation to reply)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I have revisited the possibility of corrosion on the terminal ends of the relay and in the sockets. There doesn't appear to be any actual obvious corrosion but one of the 4 terminal ends is somewhat discolored. I now believe they are all originally brass but one of them looks somewhat like it is copper. What I mean is that I think possibly one is heat-discolored or perhaps oxidized in an odd manner. I remember now noticing this awhile back but thinking it was just a differnet alloy like hot side connections on 120v plugs, etc. All 4 socket holes look fine and the same. This relay is in an enclosed box under the hood and it looks like new inside the box. All 4 socket holes look identical and normal. What is odd is there is never any cold failure of the relay. They always work if left to cool down and never fail while running regardless of how hot things are. Do these things only operate at start-up?
In any event I treated all the terminals and the socket with A-120 Corrosion Free. A-120 is basically a penetrant/lubricant/moisture displacer with a high dielectric strength sold in some marine stores to treat fuse boxes, etc. in damp high corrosion environments. It is hard to find but good stuff and comes, or did come in an aerosol can that has a yellow label that looks straight out of the 1940's. So far no start-up failures but it has been a bit cooler and I haven't given it a real test yet with a few quick stops after a real warm-up.
I think most probably the discoloration is a symptom of the problem and not the cause but I don't know. Any more thoughts now that I am giving more complete information? After talking to the parts guy at Toyota I am pretty sure that new relays have identically colored terminals, at least now they do. However all three of my rotating relays have a discolored terminal. I should have been paying more attention to this before but it is hell to get old and need reader glasses for close-up vision but not use them when driving.
Scott
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Scott wrote:

Can you visually check the wire ends under the socket terminal to be sure that they are not frayed (perhaps an intermittent short) or breaking? Sometimes wires will fail where they are crimped or connected to the socket terminals themselves that are then inserted into the plastic relay socket if it was made that way. Some are sealed and just a harness is visible.
If I understood correctly, you did mention earlier that the check engine light does not illuminate when you know it's not going to start when you turn the key. That in itself may have set a trouble code in the computer. If you have not had it scanned, that may be another possibility. You can sometimes have it scanned free at parts stores.
I took the time to look at a mid nineties land cruiser schematic and it may not be exactly like yours, but on that one, the EFI relay as well as the check engine light is powered through the ignition switch (perhaps a clue) and controls / powers the circuit opening relay that controls the fuel pump.
The ignition switch is a possibility but needs to be tested when the problem occurs with a voltmeter to check power to the relay. The check engine light will probably be out. The fuel pump is a remote possibility. Check all grounds for corrosion and clean as necessary. That in itself is a very neglected cause for problems.
Follow your wiring diagram and check to see if those components are common.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ph@Boy,
Thanks for the additional imput. I've been out of town and unusually busy and will get back to you after I check on the things you mentioned. As I recall you are correct on the wiring schematic. I also recall that I may be able to check the trouble code myself but not sure, regardless I'll make a few calls if I can't do it. I will make a more complete reply after some more work in a day or so.
Scott
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The wires are clearly visible under the socket as the sockets in the box actually sit on a grid floor. Everything looks good and they exit in a common conduit that looks fine.
I remember now why I didn't check the trouble code status before. It is because the check engine light has never come on while the vehicle is running and according to a shop manual I have, that has to happen to initiate a trouble code. Regardless I did check for the possibility using the on board diagnosis system which is easily done at home. The code I received was code #1 which is "no malfunctions".
Still looking at the wiring diagrahm. It does look like the EFI relay is in series with a fusible link. If so wouldn't the link melt if high current was the problem? I'll keep plugging and keep my fingers crossed since there have been no episodes since the A-120 treatment. However many times in the past I thought it was fixed but I think actually the ambient temperature, warm-up period, and/or cool down period were not actually aligned quite right for it to not work.
BTW every time I bought a new relay everything seemded fixed for awhile too. It seems that they degrade after awhile to the point where they will fail if conditions are right but never actually go bad all the way. I think maybe the A-120 may have reversed this process somewhat but I wouldn't bet on it. What I mean is that I think for some reason it is overheating and that for some reason causes a bad connection when hot and the bad connection causes temporary failure but I have no idea why it is overheating. The A-120 and new relays just help with the quality of connection but the heat eventually overcomes this.
Scott
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Scott wrote:

It will probably be the most inconvenient time for you, but I think that this is more than likely going to be a problem that is resolved by checking voltages when the problem is actually occurring.
You have replaced the EFI relay several times so I don't think that it's a bad part. I would suspect either the ignition switch, or the load wire from the EFI relay to the circuit opening relay, slightly or intermittently shorting, or the circuit opening relay itself, or it's socket.
You might want to examine and clean the circuit opening relay like you did the EFI relay, but I believe that the engine check light is only powered from the ignition switch, and if it is not illuminating when the key is turned on, and the problem occurs, I would suspect the ignition switch itself as I mentioned earlier, and would suggest to either check the voltage from it, or change it out.
I don't think that it's the fuseable link either, but voltage checks can verify circuit feeds when the problem occurs. Move / wiggle wires when you check.
The vehicle is fifteen years old, so it could be anything, just the number of cycles on the ignition switch, or movement of the wiring harness to it in the column (tilt feature if equipped) could have worn it out, but that is just a guess. Each individual has different driving habits getting in or out of a car.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Scott wrote:

Something you said.. "It isn't beause it heats up under the hood after shutdown because it will fail to start within seconds of shutting it down."
The way I understand you, the only thing you did was turn the key to off. Go for the ignition switch.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

What I actually meant was that a functioning relay may be only necessary at start-up. Once over-heated it may trip a self-resetting circuit breaker, as Ray O alluded to, and then reset when it cools. If very hot it will often fail to start within seconds of shut-down but will start instantly when I put in a cool relay. This whole process, meaning a hot car/turn key/no check engine light/no start/ replace relay/then starts instantly can occur in about 30 seconds if I'm in a hurry.
I'm pretty sure the no starting problem is a hot relay but I don't know what makes the relay hot . . . yet. It "broke through" the A-120 treatment and didn't start once again today. I'm considering leaving the lid off the relay box for extra cooling and ventilation to the relay though it is warm everywhere under the hood anyway. BTW, thanks again for the imput and I'll let you know if I come up with something.
Scott
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
replying to Scott, Shep wrote: The power supply wires are too small put in a heavier wires leading to your relay and it doesn't get hot and fixes problem
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.